Behindblueeyes, I have a 10 yr old son and 18 yr old triplets. Unfortunately, I am now going through my second divorce. My 10 yr old is from my second husband so we are in the same boat, age-wise. There are a few possibilities here, most of which have been mentioned by other posters.
Obviously, your daughter is angry and you're the only person she feels safe enough to express it to. I'm not sure what your ex is like, but do you think he criticizes you in front of her, or maybe the new woman does so? That was my first thought. Why else would your daughter call you a "loser?" Is your ex controlling? That could be another thing that upsets your daughter. My ex is is like that and our son is afraid to even disagree with his dad because it's taken as disrespect. (But over here, he feels a little TOO free to do so! He is also starting to talk back and such.)
Of course, any anger she has toward you and/or drinking should be addressed with the therapist. What does he/she say about your daughter's outbursts?
Divorce is extremely hard on kids. Despite that, they still need boundries. Maybe even more so than usual. Don't allow her to get away with disrespectfulness and name calling. Make sure that she knows you're in charge, not her. It is scary for a child to think they're the one in charge. They need parents to establish limits.
Also, I'm not sure what meds she's on, but some of the ADHD ones can have anger and irritability as a side effect. My daughter was on several of them over the years and she hated the way they made her feel.
You are right to be concerned -- the teenage years aren't for sissies! That's why it's important you lay the foundation now. And most important, stay sober. Raising kids is hard enough and alcohol just adds another layer of challenges.