How do I respond to elderly mother's guilt tactics?

My mother keeps using guilt tactics to get what she wants from me. She has made the choice to live 3.5 hrs away from me and my brother. I have begged her for years to move closer to us. It's a bigger city and has much better medical care. The closest specialist for her health issues is an hour away from her home. She refuses to move because she says she wants to be where she wants to be. Now she needs more medical care. She keeps trying to get me to move in with her to take care of her because she retired to move in with her parents to care for them (something they never asked her to do). She guilts me by saying that she took care of me as a child and young adult so now I should take care of her. I'm divorced and have a full time job. I am not old enough to retire and I need to work to pay my bills. I do take my PTO to drive 3.5 hrs to take her to major medical apts another hour away and 3.5 hrs home. It's a minimum of two days PTO. She does have a caregiver who will drive her to checkups and does light housework and errands for her. She constantly tells me that the (paid)caregiver is there for her and I am not. She is constantly telling me that she is going to die soon and that I will regret not taking care of her. When I told her that I was getting a divorce her response was "good, now you can move in with me and take care of me".

My brother has no contact with her now except when he needs money because of her mental tactics. He ironically has a wife who is just like his mother and controls him. He never helps with her caregiving.

How do I respond to her when she is guilting me that I can't move in with her to take care of her full time?