Maybe you were wrong about other stuff that happened, but it still doesn't mean it's all your fault that you and your mum have such a rubbish relationship.

It seems more likely that neither of you are all-right. Doesn't mean for a moment that you are all-wrong, either.

How to handle that uncertainty is the real challenge it seems to me.

Her behavior hurt you, that's likely real enough. Maybe intentionally, maybe not, but the hurt was real. Are you maybe mourning the relationship you wished you all had had? Not all your fault, there were two in the relationship. Is she still alive and in good health? Is there something you might be able to do to improve the relationship? Doesn't mean it will work, of course, but if it doesn't then you will know.