wills - getting the shaft

I'm asking this Q on behalf of my mother in law who lives in PA.
She's (I'll call her Sister A to avoid confustion) currently being shafted by her sister (I'll call her Sister B) who is the executor of her father's will. Since his death, relations have deteriorated between them. For the past 30 years, Sister A has lived in the house next door, which was also owned by her father. Since the time of his wife getting sick and passing away, Sister A has taken care of her father in every way. She paid the bills, did laundry, cooked, cleaned, shopped, etc. When he became sick, he chose Sister A as the power of attorney. Sister A made all arrangements, and exerted an extreme effort to care for him. In the past several years(5-10), her father had become more and more disappointed in Sister B and Brother since they only bothered to visit once a month, if that. He had expressed an interest, several times in changing his will, which was now 30-40 years old, to favor Sister A. Always the procrastinator, it never happened, largely because the current will was in a safe in Sister B's house and he was afraid to ask for it back. As far as I know, the will states a 3 way split, and the only special consideration for sister A is that she is not to be kicked out of the house she lives in.
Sister B is the executor named in the will, and has bullied Sister A out of keepsakes (pictures, jewelry, etc). Sister B has also removed Sister A from the decision process. Sister B also wants to back charge rent from the time of his death, and has mentioned trying to collect rent while he was living on the basis that he was 'snowed' by sister A. Also, despite the explicit term in the will, Sister B has named an outrageous buy out price, so Sister A actually is being evicted from her home since an agreement can't be reached.
My question is, is there anything to be gained by sister A hiring an attorney? As i understand, no matter how wrong the situation, there is no legal standing for a will contest. Is there any valid argument for special consideration based on her being the only individual who cared for him (in the emotional and physical sense)?

Thanks for your input in advance.

Has a probate of the estate taken place? (would be of public record at the recorder’s office) Did the deed give a life estate to Sister A to allow her to continue to live there?
I’d suggest that Sister A get copies of whatever probate took place, and have a consultation with an attorney.

"(would be of public record at the recorder’s office)"

I should have said the Probate records would be on file with the court probate clerks office.