Plenny,
Very similar happened to me. Before I knew of her drinking, she was such a good friend. We had great times together, great laughs and talked about everything. One night it became apparent she had a drinking problem and from then on things just gradually changed. Her attitude towards me, she evaded any reasonably questions I had of concern for her, she'd ring me and leave ambiguous messages leaving me worried about her then would ignore my return call. Our friendship was up and down for a couple of months before she ended our friendship and pinned all blame on me. I was the reason she drank, no-one had ever treated her as bad as I had, etc, etc.
Only through reading on here did I come to terms with what was happening. She probably felt ashamed of her behaviour and with me around they would always be someone that wants her to stop drinking and want her to be responsible for her actions. Her ability to drink in comfort was no longer the same because I wanted her to stop killing herself. I never actually questioned her about her drinking, just her actions on the following days after an episode which she would evade so well. So she made a decision and alcohol came before me.
I haven't heard from her for about 4 months and have no idea how she is getting on.
I read a quote that hit home on this forum a few days back from a recovering alcoholic who wanted to contact a old friend who they had pushed away ; "I suppose I got what I wanted, the one person out of my life that wanted me to stop drinking"
It's a horrible disease that has robbed plenty of people of wonderful friends/partners/family members