Does she KNOW about the mistakes you made? Is that why she doesn’t like you anymore? OR…was she never overly fond of you to begin with?
IF your MIL is fully aware of the mistakes that you made toward her, then apologize to her. Tell her that you feel sincerely sorry and ashamed for what you did, that you would like to start the relationship over again in a more positive way, and that you hope that she can forgive you. And then from that point onward, try to bond with her, show her hospitality, etc. Even if she shows her annoyance or pettiness, be the bigger person and display patience. That way, she’ll know that you’re serious about making things better and that you don’t want to hold grudges. Back up your apology with positive actions. Actions speak louder than words.
IF your MIL has no idea about the mistakes that you’ve made, then you have two options. I think that Islamically (based on what I’ve heard, not 100% sure though) is that if you fear that confessing your mistakes to the wronged party will only destroy the relationship and make things worse, then you can compensate by making good dua for that person and trying to go about fixing things in a more indirect way. Let’s say that you gossiped about your MIL behind her back…to compensate, you should try to say good things about your MIL to the people you gossiped to…as a way of fixing things and her image in their eyes.
********** Needless to say, your MIL is not obligated to forgive you. And if she doesn’t, that’s her right. She’s not even obligated to like you. The more important thing is for YOU to learn from your mistakes and not get involved in negative thinking/actions that would lead you down the same path.