AITA for being upset that my MIL told my husband she had cancer AT our wedding

My MIL hates me. Me and my husband have been together since we were 17. She lost custody of him when he was 8 for severe abuse and got her rights terminated. She's upset because it's too late and is jealous that her son has another woman in his life. She has constantly gotten upset when he has put me first when we were engaged. Talks about how no woman will ever love a son as much as his mother. How much can you love him if you abused him? He's been trying to have a relationship with her but keeps her at a distance.

At our wedding she went and pulled my husband to the side right before he was supposed to go to the altar and told him she had cancer. It through him off completely and when I walked down the aisle he looked distracted. He forgot his vows and after everything he told me what his mom said. I could tell he wasn't all there when we said I do and maybe I'm selfish but why are you telling you son AT his wedding right before he's supposed to be standing at the altar that you have cancer? The moment is supposed to be about us. Then we find out from the step dad that she doesn't even know 100% if it's cancer yet. The doctors think it is but they haven't finished testing. Am I selfish