What do you have the most anxiety about? Speaking as someone else with anxiety (guy though) I found that just doing it helped me out. It's leaving there and worrying about what could happen that's the worst for those with anxiety.

Once you're there, and you see how it's friendly, it calms down. At least that how it is for me. As for advice for chilling out, well, if you're gonna worry you're gonna worry, really. Just keep it in your mind that once you get there, there are overwhelming odds that you'll have a great time. You'll discover the freedom in solo travel, and the joy of being somewhere completely different, where everyone you meet is someone you know. The, you know 'meeting new people all the time' can go either way for those with anxiety can go either way, but for me, it actually liberates me from social anxiety. I don't have to worry about what people will think about me and so on, because I'll be gone in just a day. I can just meet people and enjoy it. Not saying it will be like that for you, but it can be great for some people.

Keep in mind the positives, how it can be a wonderful escape from your daily life, and stay focused on that :) Good luck and hope you have a great time.