When my mother is gone who will be responsible for her debt?

Strictly from a legal standpoint, if she had no co-signer on her credit cards, then when she dies if there is an outstanding debt, the company must file a claim against her probate estate. If she does not have enough assets in her estate to pay all the creditors, they are out of luck (it's called a bankrupt estate). No other family members would be liable for her debts, since they are personal to her.

One way to stop your Mom from getting new credit cards is to "freeze" her credit via the 3 large credit bureaus. It's pretty simple to do if you know enough about your Mom's credit history, and depending on what State your Mom lives in, the cost to freeze is $10 per credit bureau or no cost at all. Just go on-line, and click on "freeze credit" within the credit bureau's websites.

You are not responsible for her debt unless you had co-signed on the credit cards or any other type of financial document for loans, etc. But don't be surprised if credit collection companies start calling you and your siblings trying to get as much money as they can.

The money in her estate has to pay, you might be able to get them to reduce the bill. No one except a spouse would be legally responsible for the bills but they need to be resolved before the inheritances get paid.

Actually, if you gain the guardianship over this person, yes you can freeze their credit. You can have control of that along with their financial matters and even their social matters. Furthermore, you even have control of medical choices and what's best for the ward. Guardianship give you complete power and control over all matters of that person's life including their credit and financial matters

Have you talked with her about it? Save up evidence and bills not paid and talk w her a few times, to say this is a worry and you should hire a financial bookeeper now or a lawyer now - I understand someone with dementia will forget or argue, but there are often lucid times, or if you feel debts are already mounting, then you need to talk with her with the evidence maybe a few times, or hire someone to watch over her money at this stage. I've seen elders argue but accept limits when they are given to them by a financial estate manager - make the agreement that she is not competent - is one option, if the debts are just mounting and bills not paid - or if a bookkeeper would help her stay on track - she can meet with the bookkeeper every month, and go over all bills then. The best arrangements that I've seen, leave an amount in the person's checking account for spending money - maybe $500 - so that the elder is able to pay to have her hair done or some purchase, but move all other money elsewhere, like CDs or wherever. Plan the basic amount she can spend and have the agency deal with her with you then help keep her on track. Every situation is different, and she should have some discretion, but any large amounts stored safely elsewhere - and she may either agree, and it's worth the effort to help her see the value, many women of older generations are used to allowing men to plan for them, so having a male lawyer help draw up the plan or get her to agree, can help. Ask your local council on aging the names of a few legal or monetary agencies and see if you can find one that is certified or whatever, that you trust, it's worth the fees to pay for some help in this area, even if maybe starting with a bookkeeper who works directly with your mother may be all that is needed - try that first, for she may come to value the regular help.

One other thing I might add to all the good advice given here....if you are or get POA and pay her bills always put POA after your signature on checks. Also let anyone you deal with directly on her behalf know you have POA. That lets them know you are not responsible for her debt. You will be contacted by them after she passes but it will be for her estate to pay the debts. As a other's have stated it is wise to get counsel on which must be paid and which may be written off. As POA for my MIL I paid all her bills for two years. My husband was executor and he made sure ALL bills were paid before any inheritance was paid out to heirs of her estate. She had about $25,000 in credit card bills but thankfully she also had some annuities that once cashed covered all her debts. It did take about a year to settle everything but I kept in constant contact with the creditors and things went well.

I am sorry about your mom, and that you are having so many worries to deal with. Even if you are living with your mom, her debts are not your debts, unless you have joint cards or accounts. Her estate would be liable, so if she has any assets, like a house or bank accounts, her creditors may go after these assets.
I hope this helps a little bit to ease your mind.

Are you her POA ?

Castle is so right when it comes to an elderly Mother only accepting advice from a male. My Mom [98] was that way.

I remember on the forum here where a Mom had giving her son financial POA but not the daughter. The son was clueless about handling money, and the daughter was a CPA. Go figure. But that is how some women though back decades ago.

Also one's parent still see their grown children as "kids" even though we could be senior citizens ourselves who had successful careers... but what do we know :P

How is she getting around to spend her money? Don't take her shopping and don't help her with on line shopping. If you see her ordering stuff from TV, find it and send it back.