Mother in law/ don't trust her

Through my relationship, my mother in law has been condescending, rude, sarcastic & very mean and controlling to my significant other. Now, we're moved out & we have been moved out for 3 months now & she wanted him to take care of his siblings at or house 3 Times a week.... without asking, she expected him to do what she says. She's very controlling & abusive. She slapped his 8 year old sister in the face for not painting her a Xmas card on Xmas day! Last month. Recently she had a breast cancer scare (it was negative) and all of a sudden she wants to be nice to me, come over with food, calls my bf and have him put her on speaker to joke around with me. When I went over for breakfast, she made me and him food.. she NEVER did that before, btw. She even wants me to go with her to go workout jogging in the morning (we live by the beach) I think it's nice and all, but idk. I feel like after being tormented, mean to me and sarcastic with me and my bf for so long, I'm just not interested anymore. I am still very nice and courteous to her. Very respectful & I say thank you all of the time.. idk why I'm so distant from her when she's being nice. I feel like it's a catch..