In desperate need of relationship advice. Help?

A friend of mine is in a bit of a situation, and asked me to post this question on my fluther. His words exactly:

“Okay, well right now I’m in a relationship with a girl, have been for a couple months now, and really like her. We’ve both been through a lot of things and have been hurt badly before. I could say I love her as much as I am capable of loving someone right now. About a week ago, we had some problems. From what she said, I betrayed her and she was really hurt by what I did, something involving another girl and me flirting too much or something to that effect. I still don’t know what it is that I did, and she refuses to tell me. I convinced her to forget everything that I did and for us to get back to where we were before.

Since the start of our relationship, everyone except for her friends have been opposed to the relationship. Mostly because, a little over a month prior to my meeting her, there was a complicated situation I had with another girl where I was lead on and then deeply hurt and sent into a deep depression when I skipped school for about a week, and then stayed depressed for a good time. My current girlfriend has been a bit difficult in doing some really trivial things like even labeling us as being in a relationship, yet insisted that she really cares about me and just needed a little bit more time to get over some things. Because of that, everyone I talked to, even my best friends have told me that she is a tease, indecisive, leading me on, and using me. They have told me that she isn’t worth getting hurt over and to leave her. I refuse to listen to them and trust her saying that she wants to be with me and she’s not using me to get over anyone or anything like that. Now the real problem…

Apart from that, I’ve had a longstanding issue with a once good friend of mine. She, in the past year or so, had a lot of things in her life take a turn for the worse, and she became heavily involved with alcohol, marijuana, and most of all cutting herself. I drifted apart from her and wasn’t there as she got worse and worse. I want to say 3 or 4 months ago, I found myself saving her after she tried to kill herself. I talked to her a lot and tried to help her with her issues starting after that.

I had hoped that she would begin to improve to some degree, but to my misfortune, adding onto her addictions and great self esteem issues, her life began to deteriorate as most of her remaining friends disassociated themselves with her and people she knew started to sexually exploit her insecurities. Her home life began to crumble as her parents fought every day and occasionally took out their rage on her. As a result of this she dwelled upon the thought of suicide more and more heavily despite my great assistance in giving her resolve for living. It has come now to a point where she is completely reliant on me for the will to live and she has convinced herself that she loves me and cannot and will not live without me. I truly care for her well being and safety, but could never share those intimate feelings with her.

This coming back to my current relationship… This second girl is pressuring me to leave my girlfriend and have sexual relations with her, and I can’t help but feel tempted due to the current issues and everyone opposing my relationship. But inside of me I know that things will work out with my girlfriend and I don’t want to lose her or hurt her, ever. I feel myself stuck in an impossible situation, as I don’t want my friend to die, nor do I want to see anyone die. And at the same time it seems to me the only way to keep her alive is to risk losing the girl I care about more than anything by breaking my promises to her that I will never cheat on her. Can anyone give me some advice?”