Taking care of yourself is NEVER selfish. (Even though we were taught that it was.) Obviously she has no problem taking care of herself to the point that she ignores your problems. You need to protect yourself. I think you're smart, not selfish.

Some of us have trouble setting our boundaries. But it is one of the best things we can do to protect ourselves. If she gives you grief about it, just keep remembering that you have to take care of yourself first. Otherwise we have nothing left to offer anyone else anyway.