Relationship with my mom is staining because I don't know if I can be her caretaker

My mom is 78 and she has been guilt tripping me to be her care taker. She is currently living with my brother to help raising his kids.

She constantly tells me once they are old enough, she will move in with me so that I can take care of her.

The thing is I don't know if I am capable. I can't guarantee the future.

I also don't want to shoulder the financial burden. She has money but she wants me to pay for her expenses so that she can leave (my brother's) a generous inheritance. She always tellsd me I won't get anything since 'i have no kids and I have enough money, and he needs more."

Now we are not talking. It hurts. Why can't she understand not everyone can be a caretaker? Why is she expecting me to help raising his kids indirectly?