Does my mother have any rights to dispute her "incompetence?"

Your bros are not qualified to declare her incompetent. To be on the safe side see a geriatrician to assess her competence and get it in writing and send them a copy. I am sorry you are going through this, We see many cases of greedy sibs who do nothing to care for their parent but want their money and abuse the care giver.

BTW who has POA for your mother? If she is competent she is handling her own finances, but it would be good for her to appoint you as POA medical and financial for the time when she cannot do it herself.

People are not "incompetent" on the say-so of a relative. That designation is made by a court based on evidence from doctors and other witnesses.

If she were declared incompetent, what do your brothers intend to do? Care for her themselves? Place her in a care center? How is having her incompetent beneficial to them financially (in their minds)? Does one of them intend to become her guardian? I assume you would contest that and if family doesn't agree the judge may instead assign a professional guardian, who would be paid out of her funds. The guardian (professional or family alike) has to keep careful financial records and report to the court. Not a lot of opportunity there for fraud. I hope your brothers realize this before they spin their wheels any more.

To whom are your two brothers reporting this so-called abuse?

Was deleted since this was a duplicate post. Please read my next one.

It sounds like to me that your brother's want to have her be declared incompetent so that they can take any power you may have in your mother's interest or decision making away from you. Usually it is always about money especially from those in the family that do nothing to help. I also find that it comes with a lot of jealousy when one sibling has the POA or are the trustee. I think maybe this is because you stand in resistance to what they want to do. If they truly cared about your mother, they would be helping, unless of course they are incompetent or disabled. But being a trustee and having the POA for my mother, I can tell you  from personal experience  that it's a thankless job and so don't expect things to get better with them. I would suggest though, if you have no legal Authority that you become her guardian or like the previous poster said to get both the financial and health power of attorney since you have no grounds to speak in her behalf. Since any family member can take her to a doctor and have her declared incompetent if she is, then I would be looking to get it started ASAP. I find that my 90 year old mother talks about marrying someone else and there's people out there that would take advantage of that just to get any money or property she has. Like you I haven't taken a dime but that's not going to count if someone convinces her to sign over everything to them and she hasn't been declared incompetent.  the court may feel that she is responsible for her own decisions however bad they may be. My 90 year old mother threatens to get married and there are people out there that would take advantage of that if they thought they had anything to gain. However,  my mother has been declared by her doctor and in writing that  she  is incompetent because of her dementia/Alz  and is unable to live on her own or take care of herself.
Sorry for what you're going through since it takes a lot out of you.. not an easy job!

It's the way the headline question is phrased that gets to me. Does a person have any right to dispute [an allegation of] her incompetence?

Consider the following hypothetical scenario:

John Doe: You are not of sound mind!
You: Oh all right then, if you say so.

*Of course* a person has a right to challenge the opinion that she is incompetent!

But the OP's very anxiety and hesitation over what should be blindingly obvious leads me to suspect that there is a lifelong habit at work here, of deferring to her overbearing brothers. And if that is so, there is abuse in this family: her brothers are in the habit of abusing people who stand in their way.

In a guardianship proceeding your loved one would have a court appointed person to advocate for her best interest.

If she has not been declared incompetent by a doctor, then she's competent enough to make her own decisions. It sounds to me like maybe she has considerable wealth somewhere or something of value someone wants and it seems like someone needs to take over her financial affairs. Definitely get you an eldercare lawyer and go before a judge on this one. Get all the hardcopy documents you possibly can and strengthen your case by showing all the proof you possibly can. As long as the elder is competent to make her own decisions, she can do whatever she wants and go wherever he wants. You can also call the APS and tell them of any threatening situation that may be occurring. 

Finally, I should mention that in light of Carolgigi's mention of guardianship, there are monsters out there, not every guardian is fit to be a guardian. Even some of the court appointed professionals can become monsters when they have control of not just the person, but also their money if they happen to have a considerable amount. Be there he careful who gets guardianship of your love ones because you never know who may become a monster

Hi. I had to hire an attorney and take my mom to court to have her declared incompetent so there is a complete legal process that has to be followed. Having someone declared incompetent is or can be in depth. The courts here hired three non biased professionals to visit with mom to decide what she is competent to deal with. They found her totally incompetent. I obtained guardianship but it was one of the hardest things I've ever done. I cried all day. They (your brothers) cannot declare her incompetent. Good. PM me if you need more info. Good luck!

I hope no one is abusing your mother. As soon as you can establish that she is not being abused, then you can move on to whatever problems you and your siblings may have.

In my experience you can be accused of abuse but that does not mean you abused your Mother. If there is no finding by a court or an agency that you abused your Mother it can damage your reputation and hurt your Mother if your brothers succeed in separating you and she. If you have a witness to the slander you can get an attorney. If you have a witness to how well you are treating your Mother see if they are willing to put that in a letter and send it to your brothers or have them talk on the phone with your brothers. What will happen to your Mother if your brothers succeed in separating you and your Mother. They need a wake-up call. If your mother is put in a Senior Care Facility in Independent Living the cost can be $2,500 per month more or less, and if your Mother needs a higher level of care it can easily cost $4,500 + or - plus and if she needs a round the clock Nurses Aides they charge $25.00 per hour. This runs over $200,000 extra per year. Even if the Nurses Aides do a good job it is still not the same as having a daughter or son taking care of the parent. With memory problems it is usually the short term memory that goes first. A Mother remembers a offspring caregiver from when she or he was a child and can feel the Love of the Lord coming through because of a link to the past.
Family members can start treating you very well once they realize all the benefits of having you care for your Mother. Keep trying to get your brothers to see the light. It is a good good thing for family to be on the same page. Praise the Lord.

yes, you can be falsely accuse you of anything. If someone wants to accuse you, make them prove it! If you're handling money for starters and have good records proving where the money went, they can't accuse you of financial abuse and if they try, it won't stick. If you're ever accused of physical abuse and there's no police record, it can be your word against theirs without witnesses. The same goes for any other abuse type, make accusers prove it

Then ask your brothers to prove in a court of law any "faux" abuse. Under no circumstances should you show them any back records of your mother's.