Dear Utterly Confused,
Let me clear up your confusion:
- Don't speak to her any more.
- Don't see her any more.
It'll Be Difficult
It'll be difficult for a bit, but you'll recover, and I bet you'll end up finding a good female friend eventually who will appreciate you for the loving, caring, selfless person you seem to be, and she'll want to be in a committed relationship with you.
It's Not Healthy
Jennifer DID use you -- as a crutch, a shoulder to cry on, whatever you want to call it -- she took advantage of you. I'm not saying this is typical, or that only women do this to men. It happens both ways. The point is, it's not healthy, it's not right, and no one deserves it.
There were a couple of red flags in your letter, too, which clarified things for me. Namely, the jealousy and the alcohol factor. If she was only able to truly show her emotions when she'd been drinking, she's got issues to deal with that would be best addressed in the care of a professional therapist and an alcoholism treatment program.
Her Jealousy is a Problem
And jealousy feeds off other jealousy. I have a feeling that if you were with a woman who wasn't insanely jealous of you seeing platonic female friends, you wouldn't freak out over her hanging out with male friends.
I'm Also Too Nice
So call this a lesson learned, take some space and time, and be yourself. If you're really as nice as you say (I have the same syndrome), you will find your intended and be happy. Don't stress over it -- you're still young.