Caught my FIL cheating

So I just caught my FIL cheating however I'm not saying anything because my MIL is a bitch. She denies me and my SO's kids because they are darker skinned than her and her little lighter family. She tried hooking up her friends daughter with my husband even though we are married. She constantly tells my husband he could have done better. She's honestly horrible. Cheat on FIL cheat on. She deserves it