Four-time fumbler wants to not fumble

People of reddit, I am a chronic fumbler of my own creation and I need advice. I met this girl on a uni trip back in April and we got along swell. She's super interesting, funny, and pretty. We even went out once (I intiated but forgot to put on the "date" label). I invited her to study with me a couple of times as well and she agreed (once again I initiated but said nothing more). I noticed her interest slowly disappating until eventually I sent her a message and she just didn't respond (it has been a month now). I still see her occasionally but only in group activities. Am I cooked? Do I try to actually ask her out on a date (and actually say the gosh darn word!) or should I take the situation for what it is?

I am 23M and she's a couple years older if that has any importance other than she probably wasn't a fan of my nonsense