I hate my bfs mom

I don’t wanna say hate but I dislike my boyfriend mom a little back story I knew my boyfriend momma before I met my boyfriend and we got along just fine she actually was trying to hook us up so a couple months in are relationship people started telling her shit that was not true about me she believed it and started saying all these bad things about me and acting funny when I came around but I always brushed it off and was trying to get her to like me but after a while of me trying I just stop giving a fuck you don’t like me ohhhhhhh well I’m not kissing no more ass eventually she got Cordial With me just because her son distance himself from her because he saw how she treated me so I go over her house for family functions you can tell she don’t want me around honestly and I honestly just cant brush off the things she have done and said about me it’s got to a point I don’t wanna be in the same room with her I don’t wanna be in her presence but my bfs very family oriented and I go to the family function to make him happy but I’m tired of putting on the fake ass act I don’t like you n you I don’t like me period

My question is how do I tell my BF i don’t wanna be around his mom

Pretending I’m sick every family reunion or holiday is getting old af 😂😂