So long story short

There’s this girl I met last semester in university ( she’s 22 and I’m 27) and in class we would always sit next to each other (if I came late, I’d sit next to her / if she came in late she’d sit next to me). We’d always laugh and chat during and after class. We even met up during the study vacation to prepare for our exam (although we did little studying and just went to the bar for tacos lol). We’ve been in touch over the past month (holidays) and although I went to the USA for 3 weeks we’d always text each other.

Anyways, we were talking a few days ago online and I asked her if she’d like to grab a drink someday this week before the semester starts, she read it but she hasn’t replied. However she continues to like my instagram and Facebook posts... I’m confused, what do you guys think is happening on her side?

PS. This isn’t the first time she does this. I texted her to see if she wanted to go out for bar trivia after we finished our exams and she didn’t reply until around 5 days after when I was in the USA, she said she was sorry about that and we continued talking.