the girl (26f) that I'm (21f) talking to won't meet up IRL. I'm starting to get suspicious

Okay so maybe I'm overly paranoid but part of me wonders if maybe she has a relationship. I have absolutely no evidence. She says she lives with her mom and siblings but is never able to slip away for even a phone call. We've been texting for like 3 or 4 weeks and I keep trying to ask her out and even tried inviting her over a couple of times. Idk, she's really cool and I enjoy talking to her but idk.