Okay, so there's this girl at my college who I've met in group settings a few times. Last week I found her studying alone, so we talked for 15 minutes or so, and I got her number. It ended with me suggesting we hang out sometime and "Yes!" enthusiastically from her.
A few days later I text her, saying that we should go to the local fair together the following week. She answers with "Maybe! I don't usually know when I'll be free until a couple days beforehand, but it sounds like fun!

"
I might have screwed up at this point by not texting her again for a few more days, because the next time I saw her alone (and studying), we talked for a while and I asked if she was still up for it. She said she had an exam the following Monday, so she wouldn't have time, but again "it sounds like fun!"
What should I do at this point? It's kinda hard to tell whether this is legitimate, since a lot of people study really hard here. I'm thinking I might not have built the comfort level enough, since we've only really talked twice, aside from lunch with a bunch of other people in the cafeteria once and a "Hey!" and a smile when we pass in the hall. She seems encouraging, but I have a tendency to over/underestimate attraction. I'm not sure . . . advice?