I feel you as someone with social anxiety.Yeah I would encourage you to talk to her more. Build more of a repo with her, overtime. If you find a common interest mention about going together sometime and see how she responds. think it’s fine sending a FB friend request, it’s not that big of a deal, however I would ask her out in person. You can also better gauge her interest. I have let what “could have been” relationships slip because of trying to protect myself from possible rejection, because of my low self esteem in my mind I was doing my heart a favor. Don’t do this. It leaves room for “they like me, they like me me not” mentality and it’s just not worth it. I know it’s hard, but you GOT THIS. Even if things don’t work out you will be assured you did all you could and it just wasn’t meant to be. Just talk to her, for real tho a smile goes a long way :)Good luck!