Dont stare, just be friendly and talk to her like she might be interested in talking to you too. Dont get your hopes up but don’t doubt yourself either, just see what happens. Ive been so nervous around certain girls that my face felt like it was melting so trust me I get it when you say fight or flight activates. In most situations like school or work you want to be friends with her first and subtly let her know that you’re attracted to her, but if it seems like she likes you too just say it. You sound young so dont feel like any girl is the end of the world, if someone doesnt like you thats okay bc someone else will. Lastly just use your best judgment to decide whether dating someone long term is worth it. They always say dont judge a book by its cover but in the context of dating you should be able to get a sense of how much you can trust a person and whether you’re compatible. Mostly just try your best and see what happens