Rules for kids

Okay my loves I need advice on what type of rules should be set for a grandparent who’s a narcissist and manipulative, also just two years ago took her other son with drown syndrome to Walmart and stole, then blamed it on his disability. My boyfriends childhood trauma is all from this lady! But my boyfriend insist on her being in our child’s life, therefore I’m pregnant and have the WORSE case of brain fog I grew up with this same issue like my boyfriend but I’ve cut my father off completely, everyone is different and he just searches for the mom in her that he’s never received. Therefore I’ve tried to come up with rules I got as far as She will not be alone with our child, all these rules I will talk to him and communicate about it but unfortunately he’s not going to help me come up with things! So what rules did you have to set with your kids around someone like this? Thanks for the advice and help!