AITAH for inviting my ex's mother to my wedding, despite his wife not wanting me to?

throwaway,

My ex(31M) and I(29F) broke up three years ago. We had been dating for two years, though a part of it had been long-distance, and he told me he was still in love with his college ex, and was going back home to be with her. And that he had ended up cheating on me during one of his trips back, and he didn't want to lie to me anymore. There was more followed up by him saying I'm better off being someone else's 'good wife', and told me not to tell his mother what happened and to lie to her and say it was mutual.

His mother and I were very close. My ex had introduced me to his mother within the first month of dating, and I adored her. She is a lot like my own mum, and she is amazing. We even had weekly video calls with her (both of our sets of parents live in India), and whenever she came to stay for months with my ex, and when I went back home to our country to visit my parents, I spent a lot of time with her. Even when my ex and I broke up, it hurt a lot more because I lost his parents, whom I had come to love a lot.

His mum had very strictly told her son that she doesn't care who he marries (she and his wife don't get along), but she won't cut contact with me. I still call her at least once a month. I have gotten engaged, and have started planning my wedding, which will be held at my parents, back in my hometown. My fiancé knows about me being close to my ex's mum and doesn't mind at all. In fact, he is the one who asked to invite my ex's parents, and I thought our relationship had nothing to do with my ex, so I invited her. She was already very happy for me when I told her I got engaged previously, and told me she would definitely come to my wedding no matter when.

My ex called me a week back, congratulated me on my wedding, and told me his mum coming to my wedding had caused a fight in his house. His mum and his wife don't get along and though he has moved out, his wife thinks his mother coming to my wedding is an insult to her, and maybe I should have asked him before sending the invitation. I told him I didn't care what he and his wife thought, and no one else thinks that way only him, because he feels guilty for cheating. He apologized once again and he asked me to please explain to his wife that me and his mum were just close. I told him I wouldn't speak to his wife (she was awful to me), and cut the call.

My fiancé is mad because a simple invitation to someone I love to my own wedding should have nothing to do with my ex or his wife. But one of my own friends, whose MIL prefers her son's ex, told me how exhausting it is to deal with nasty MILs and I should have thought about another fellow woman. I didn't really think that far while sending the invitation. AITAH?

Edit: My ex and I are both Indians. I have lived here for 8 years and studied and worked here. My ex went back to India four years ago to be with his now wife. He and I were together for a year of graduate school. My wedding will be held with my culture's rites back home. My ex and I are from the same city, which is why whenever I went back home in those two years I would go to meet his mother.