It depends on how one asks... technically it is not the FA's job to help with luggage and there is liability issue if she gets injured.

Some FAs will help, some won't. In my experience there is a better reaction to "Excuse me, I had a surgery, would you mind helping me with my luggage" than to "Would you get my luggage in the overhead bin". Plus - if someone is unable to get on the plane on their own, airports provide wheelchairs and then the person helping WILL deal with the overhead luggage as well. If one chooses not to use help, they cannot blame anyone for not helping.

Even though someone will most likely help, I would say that if she cannot lift the bag, she should check it in and not carry on.