when i was 12...

Im sorry to hear about that. Its hard when parents do things like that.

One thing is for sure, it ain't your fault. For your mum not to speak to you for a year well she sounds pretty immature to me. Family should come first over her partners. Bottom line is this is life, it's not always easy, but just take comfort that you are not alone and underneath any issues you guys may have, she loves you deep down as she is your mum after all. HTH :-)