Legal Question in Real Estate Law in California

Unfortunately she is in a really challenging legal situation. If her brother no longer has mental capacity to give a durable power of attorney, it wouldn't be valid anyway. In addition, the holder of a power of attorney is prohibited from "self dealing," i.e., doing anything for their own benefit using the power of attorney. The way to get around the lack of mental capacity would be to have her appointed as conservator of her brother. However, she would then be subject to the same no-self-dealing rule as the holder of a power of attorney.

As I see it she has two options. If there is someone else who is willing to apply to be the brother's conservator who agrees that she is entitled to the house, they could apply to be the conservator of the brother and then deed her the house. That would be a very risky course of conduct for the conservator, however, if any potential heir of the brother disputes her claim.

The safest option, but at very uncertain cost, would be to bring a quiet title action. This seems like a classic case of a purchase money resulting trust. If the brother does not contest it, the cost would be fairly modest and I am sure arrangements could be made with an understanding lawyer for payments out of the value of the house somehow. If the brother contests it, however, it could turn into costly litigation. Unfortunately, without the brother signing a deed, I can't see any other path that would get title in her name without the validity of the transfer being open to challenge, and/or considerable tangential risks of adverse claims and litigation.