How to get over my moms death?

Mmk...well...It's been a few months since my mother died, I was 11 at the time ((i turned 12 a month later)) She O.D'd (overdosed on meth and pills ...)) she wasn't doing the drugs for a while but idk what changed it and made her start them again but anyways.. i watched her die and she was talking to herself and i just keep hearing the words she said over and over in my head and it just kills me. Im angry with her for leaving me but really i know that i just miss her. I personally think that im in denial about anything because i have to be strong for my grandmother since shes all i have left my father hates me.. so.. i had to move all the way from Montana to Greece but i see my mother here as well cause the first time i came here when i was 9 i came with her so .. everywhere i go i see her and it drives me crazy .. im getting tot he point where im not eating or sleeping which i know isn't healthy but every time i think about food i feel sick and every time i try to eat something i gag O.e i try to smile and say nothings wrong when EVERYTHINGS wrong .-. i try to think positive but the one thing is im pretty much sure ((in questioning)) that im a atheist.. so i cant just be like "oh shes with god shes in a better place" when im really thinking WTF eh... any suggestions how to get over her without the whole "god" thing or making it worse in any way?