What can my mom do if her husband abandoned her?

She needs to meet with an experienced probate attorney.

This is not a family law question, since they are not getting divorced. It's an estate question, and I don't do that work. You should ask your question to an estate attorney. However, if she is the beneficiary under the will, she will receive everything, unless he changes the will.

He is going to die soon. She needs to consult with an attorney and not rely upon an answer from an attorney on the internet from a question asked by someone else. Too much room for misunderstanding here. We do not know all the facts and all we can say to her is get to an attorney.

Complete answers to your question require much more information after a lengthy conversation between your mother and an attorney. If she has a power of attorney from her husband, that will be valid until he dies and the Will controls most things after his death. But, an attorney will need to review what other assets exist to determine whether the Will controls. And, of course, if he is still legally competent, the husband can revoke the power of attorney and change the Will if he chooses. Your mother's legal options are either to file for divorce or request to be appointed her husband's legal guardian if he is not legally competent. Choosing one of those options, or doing nothing, requires her to get the advice and assistance of an attorney.

It depends on the terms of the will.

If he has a will the terms in that document controls. There are many issues I cannot address as there are not enough facts. What ever separate property he had will go to whoever he chooses. If property is community, meaning it was acquired during the marriage he can devise 1/2 away if he chooses. You should consult a probate attorney regarding your specific situation. If you have a copy of the will take it the attorney.

She is entitle to her '50 per cent of the community property plus whatever he gives to her of his community property in the will.