Book Of Likes Faces

I have been my mom's "confidential" since I was a kid, almost like her "little mom". Yesterday she showed me a side of hers that made me speechless. There's a woman who is my mom's friend and I grew up playing with her younger daughter since we were close in age. She always treated me very well and like I was part of the family. I crossed paths with her a couple days ago and she vented that since her husband died 2 years ago her daughters abandoned her and treat her very poorly. I told my mom yesterday what she had told and that we should pay a visit her someday since she looks like she really needs some company and a shoulder to cry on. Here's the reaction of my mom:" since her daughters abandoned her and she's getting sick and old we should visit her and offer to take care of her in exchange for her house when she dies and you are going to help me". I could not believe what my ears were listening. Her first reaction to her friend struggling with family issues is to want to take advantage of her when she's in a very vulnerable state??? I told her we shouldn't do that because it wasn't right, one thing would be to take care of a sick and old family member and them leaving the house to us but this is too much. Then she kept saying how her daughters clearly don't deserve the house, they probably wouldn't want to take care of their old and sick mother since they don't even visit her anymore. I really don't want to do this, it just feels so wrong, I don't want to take advantage of someone who was always super kind to me. She said it was fine since it was pretty common in our country for people to take care of someone outside of their family in exchange for their house. But it just doesn't sit right with me. I wonder if this is common in other countries and if people are generally ok with it. I don't want to be part of this but when my mom really wants something it's hard to change her mind. I don't know how to change her mind about it.