How sad. I dont know how old u r or why you don't see your mom, but i am sorry this is happening. I have a stepxdaughter who we have not seen for almost 7 years her mother hid her from us and told her lots of stuff that wasnt true about her dad and i now she refuses to have contact with us. It breaks our hearts every day. So though this is a different situation i certainly understand u missing her.

have u tried talking to her in the brief times u do have with her and sharing how much this hurts you?
If u feel comfortable with it feel free to share more info with us here, someone may have ideas to help u cope with this.