When to draw the line!?

I'm posting this here here for advice, not so much controversial. I recently left a good family in Scotland to join my husband and his family in the US. He's never had a good relationship with his mum, his aunt raised him because she was incapable. He warned me about her but I thought he was exaggerating..he wasnt! She only comes over when he's at work. She's addicted to all sorts of pills and I would say she is mentally ill. She's also a compulsive liar. Anyway that's not my issue right now, she lives with my BIL who is like eating himself to death, he's morbidly obese and she has never tried to correct the situation..in fact she enables him. She treats him like a baby and hes 25. That's not even it, they have bed bugs and do nothing about, knowing they're infecting other people. My husband banned them from coming near us, but trying to be a good person I over ruled it. I bought bed bug solution and anytime they visited I would hoover and spray everywhere but had never actually seen one. Well last week after she left I was inspecting the area and there was one running across my carpet 😭😷 How bad must it be when they're dropping off you? I feel like I cant take anymore, and I know if i ask her not to visit she'll lie about me to other family members but that's the least of my worries right now. Would you ban your MIL over bed bugs? My family back in Scotland know nothing about any of this because I'm honestly embarrassed and it'll just make them worry more than they already do!