I have an incredible fear of social situations. I'm so scared of being in a small room with people I don't know that I end up getting very nervous and can't go. This has happened to me several times when I have wanted to go to Spectrum, my university's GSA. I would go with one of my GLBT friends, but he has a class at that time. Usually when I end up going with someone, my anxiety is less intense. I don't know what to do, but I do really want to get involved. The other week I went to the GSA office and spoke to the president, and she seemed really nice. It's amazing that I haven't yet been dx'd with something like Social Phobia or Social Anxiety Disorder.
All I can do is say that you aren't on your own. I had the chance recently to go to a group and completely lost my nerve due to feelings of anxiety. Its a recurring problem and leaves me feeling totally inadequate. What's the point in continuing to try when all you do is fail and feel worthless afterwards? That's how it leaves me anyway.
So you DO know someone who will be there. Go and sit with this person. In fact, you could even go to speak to her again and let her know that you have this fear, and ask if you can sit with her. I'm sure she'd be fine with that, or she can introduce you to someone else who you can go with.
I went to one and had a really hard time. I felt like a complete outsider as soon as I got there, I was quiet for most of the time and the coordinator kept staring at me like I was some sort of wacko. But I think it was me being the only closeted guy there what made me feel so different from the the others, if that's not your case perhaps you'll feel better at the meeting.
Even better thing, often the executive of the GSAs usually offer to those who are afraid, they will offer to walk with you to the groups . So message or go see her and ask if she'd walk with you to the group.
i know exactly how you feel, i do the same thing. but sometimes the best help is literally just forcing yourself to do things because you will end up having fun and that will slowly start to counteract the fears.
At least you 'have' a GSA... Even though the people at my college campus are pretty accepting, I could use one for other things. Take the opportunity. Sometimes you have to 'force' yourself to get out there. I had social anxiety before as well.