I have such a problem with my mother-in-law. I don't get along well with…

I have such a problem with my mother-in-law. I don't get along well with her because when we lived together she didn't give me any space. She would yell at me, point fingers at me, and when I was sick, she said I was lying, accusing me of deliberately not getting pregnant. But the truth is different. She has a son from her second husband, he's 11 years old. He has diabetes and some other problems. She's on pension, so I always leave my son with his mom (my mom is also retired). And that's when my mother-in-law subtly suggested I leave him with her. But how can I tell her I don'