She has blocked you and you have acknowledged that it is for good reason. Leave her alone. Her new relationship is none of your business even if he is cheating on her. I would potentially tell a mutual friend if you have one, but you absolutely shouldn't be trying to contact her.

I mean... she warned you that she was an emotionally unstable flake up front OP. She even gave you a practice run prior to you getting married. I'm not sure what you were thinking or what advice you need, other than DON'T MARRY A CRAZY PERSON NEXT TIME.

Parents don't like to be undermined. Especially by the inlaws, even if they are being homophobic towards their child. Speak to your brother about it and go from there.

Can you maintain a relationship with your brother and Nephew without her? If so, I'd take it as a win that you don't have to be around her. She sounds horrible.

Bro, we all work at Wendy's.

I can't imagine she would invite you to turn up whenever you want if she had an affair in mind. She'd make sure it was only when her husband was out, surely?

That said, if you're uncomfortable with it you don't have to visit.

That's how it starts.

Partners being jealous of closeness to family members is the BIGGEST RED FLAG of them all.

Run away from this woman. Fast. Very very fast.

She is trying to isolate you from your family. Next comes control. Then abuse.

Leave.

Who the fuck invited Maud Flanders?