trying to talk to a girl in my class ideas?

forgive me for the silly scenario and the stupidity behind it, but I definitely lack when it comes to this field lol

essentially, there’s a girl in my <12 person college class and she walks the same route as me to the same building after class, but the whole semester we’ve mainly just barely acknowledged each other. last week she tried to have a whole conversation with me while walking after she saw I was going the same route, and I genuinely enjoyed it but felt I was not acting best and left half way because embarrassment/stupidity. our class meets on Tuesdays and Thursdays, and this happened last Thursday.

so today I was amping myself up to go talk to her after class and this time go maybe talk with her in the building we both have to go to as well, but another guy ended up wanting to walk/talk with me (very rare but still happy and grateful to have talked to them lol) and the girl walked around us while walking and just somewhat ignored us, besides maybe I smiled at her which she grinned back or so. I was hoping to catch up after the conversation I was having but it lasted a bit long and now I’m somewhat stuck again. I think the obvious would be wait it til Thursday and try again, but I guess part of me is wanting to secure it better somehow or prevent that from happening again and am tempted to message her (would have to likely be via following her on insta and/or dming her, but I very much know that looks terrible usually so hence why I’m heavily second guessing it).

I know I’m heavily overthinking this, I more or less have not had terrific many social interactions in the past few years so any help on this would be awesome. thanks for your advice!