My mom lives alone and is able to care for herself in most daily things, but she falls, forgets meds, gets mail alone outside. Any ideas?

Mom really should not be living alone at this point.

If she need to have an arm to steady her...she needs a walker. "Helping" her like that will just have 2 people down on the ground. And if she will not use a walker you need to learn how to guide her to the ground NOT stop her from going down.

If she forgets meds, falls and goes out to get the mail alone she really should not be living alone.

You have a few options.
1. Have someone come in to help out daily. Remind her to take her meds and makes sure she does. And in general monitor her for falls, helps her get the mail.
2. Assisted Living facility or Memory Care where she can be independent but can get help when she needs it. (If you opt for AL she will eventually be moved to MC so choose a place that she can transition and not have to move to another place.
3.Have Mom move in with one of the 3 (or one of the other siblings). Notice I put this last on the list of options.

You mention she has Dementia..This will not get better. It will get worse.
She may go to get the mail and wander off and if lucky will be found by a neighbor or police.
The falls will become more frequent chances are she will break a hip, arm, shoulder. At that point surgery, rehab and with dementia rehab is difficult. The result may be that she would be in a SNF if she does not gain function fully.
And it does not sound like she is safe where she is. I would disable the stove/oven have her use the microwave and if possible get Meals on Wheels to deliver. At least this way someone would be checking in on her at least daily.
And you might want to think about getting cameras in the house so you can monitor her until a decision is made on the next steps.

Don't put your arm through your mother's to prevent her falling. You won't stop her falling, if she's going to, but you might well dislocate her shoulder.

This is apart from the obvious point that people grabbing hold of you in general is disagreeable, even if they are well-intentioned. Would you like it if someone did it to you, without your say-so?

A physical therapist can show you this technique - your mother takes hold of *your* arm, and you put your free arm around her, across her back, so that you're holding her hips up against yours.

E.g.
You on left, mother on right.
You hold up your left arm.
Mother grabs onto that and holds tight.
You place your right arm around her waist/hips and hold her close to you, firmly but comfortably.
You set off on a sort of three-legged race basis.

Filling the house with smoke is not necessarily a big deal - done it myself, regularly. But there are TWO points there which are a very big deal indeed. One: is there a smoke alarm? Is it working? And two: leaving the electric stove on. Especially if you might return to it and not realise it's hot, God forbid, shudder...

Anyway. All in all, you want an Agenda.

Falls. Will your mother's GP/PCP suggest a walker, rollator, or any other kind of anti-falls aid? Would she be more likely to use it on professional advice?

Medications management. What meds are these? Have you considered one of the many types of dispensing reminder box, or consulted her pharmacist about it?

Cognitive assessment. If these difficulties are all part of a pattern that has recently come to light, it would be sensible for your mother to have herself checked out by her doctor. I'm guessing she's not going to do that to please you, correct? I'm also guessing that you don't have HIPAA authorisation - she hasn't named you as someone to share confidential medical information with? But you can still write to her doctor and share your concerns with him/her, even if you don't get immediate feedback. You then do some nimble talking and get your mother along for an appointment, any old appointment, and leave it to the doctor to explain.

More generally, your mother seems to be feeling "got at" and criticised for these "little" niggles; whereas all you want is for her to take her own wellbeing seriously and accept help where it's wanted. For now, anyway [you don't say that to her!]. I know how frustrating it is, but every time you talk to her remember how sensitive she is about it, and try to reassure her that you're not about to have her bound and gagged and dragged off to a nursing home. This is all about her *staying* in charge.

And, of course, she may herself be petrified at the idea that she's "losing it" and doing all she can to ignore problems. You can't blame anyone for dreading the loss of their faculties; but the answer to that is always - better the devil you know. If she faces up to aging, which comes to us all, and finds out where she stands, and takes some basic precautions, then God willing she'll get to make choices she's happy with.

I think you already know the answer to this. Mom needs help. None of us Seniors want to accept the fact that we are aging. I hate the fact that at 65, I’m slowing down. When our kids tell us we need help, our first inclination is to disagree. We know we need help, but we sure aren’t going to admit it.

But, in your mom’s case, she’s putting herself in danger. When I came into my mom’s apartment once and she’d left her oven on, I knew then she needed help. Falls can be deadly. They happen in a split second. If we can right ourselves, we may get away with a pulled muscle or a few bruises. But, we might also hit our head or break a bone. In addition, your mom could start a fire and endanger the lives of others.

A kind and loving intervention might work. If you know a good friend of her’s, maybe ask them to start a conversation and mention how great it would be to live somewhere (like a senior apartment or Independent Living) where there is access to help and senior activities. You and your sibs can also speak with Mom and firmly but lovingly tell her you’re scared she will get hurt and you’d be devastated if something happened. But, you cannot force her to accept her aging. If her mind is sharp, she will continue to deny anything is wrong and you will have to be super vigilant until she, herself realizes she needs assistance.

At the least, maybe a Life Alert subscription?