My Dad is 72 years old and my sister is using him for everything from a personal driver, to buying her groceries and kids medicines, and paying her rent! My Dad is starting to frail, but she doesn't care. She uses manipulation & pity to get into his pockets. She is verbally abusive to him, and threatens that she will not allow him to see his grand kids. Others are starting to notice as well. I can't just stand by and watch her take advantage of him. My sister and I are not on speaking terms. And my Dad just doesn't get it. I've tried to speak to him about it and he shuts down and starts to cry. He's decided to sell his home. And he must use her lawyer! How do I help this situation? Any advice appreciated! Thank you in advance!
Other than that, everything depends on your father's mental capacity. If he is in full possession of his wits, he is a consenting adult and the law assumes that he is capable of making decisions and understanding what the implications are. In that case, sad but true, while your sister's treatment of him is on the face of it disgusting, it is not illegal.
When you say "others" are starting to notice as well, who are these others? Is any of them someone who might have some influence over your sister? Especially in close relationships, the way you treat a person tends to become a habit, and that habit tends to become more ingrained over time, for good or ill. It could be that a timely wake-up call, a "what do you think you're doing?", given to your sister by someone she respects could stop this getting totally out of hand.
Is your sister married? Is there anything about her circumstances that would explain why she's behaving in this appalling way?
Why does your sister need to call on your 72 year old father for help with her rent, her groceries, her kids' healthcare and driving services? What is going on with her?
The attorney may have no idea what the daughter is doing. If he/she doesn't back off (ask for a response to your letter), consider filing a grievance with the State Bar Assn. All family members that support you should sign the letter. Most attorneys I know don't want to get involved in family feuds.
I think the bigger questions are (a) why is this daughter so manipulative and abusive, and (b) why is your father unable to stand up to her? That's not a criticism of him; it sounds as if she's very domineering and intimidates him.
Family needs to join forces and put her in her place, and support your father. Is anyone else standing up for him?