Has she lost interest ALREADY?!?

OK, I liked this girl and she seemed to like me. Here's how the whole thing went down (copied from a question that I asked 2 days ago; today's question is at the bottom) :

"I went out to the movies with my best friend (we'll call him john) and his girlfriend (we'll call her tracy) about a week ago and they brought along a girl (we'll call her amanda, one of Tracy's close friends) that I hadn't seen in about a year since she left my school, and man did she look cute. We watched the movie, went out to dinner, I talked to her a little bit, mad her laugh a couple of times and everything was cool. Well, 2 days later after my graduation Amanda (which according to tracy, had wanted to come but her parents wouldn't let her because she was grounded) had been wanting my number ever since the last time that I had saw her. So we made another movie night and I got her number with no problems. I went over to her house one time because we were waiting for other friends to show up so we could all chill, and amanda and I talked for about 40 minutes and she seemed shy, but we talked ok. Now, I've been texting this girl for the past 4 days and we seem to have a lot in common, and for the past 2 nights she always says "text me tomorrow :)" (does this in particular show a little bit of interest? (We text at least 50 or 60 texts a day) I'm starting to feel more comfortable talking to her and I even told her that I liked talking with her and she said the same about me. Sometimes, she will start texting me without me prompting her to. I feel that I'm learning her a little better and a little bit at a time, but I really need to ask her out on a date to get to know her better. I will be seeing her today when I pick her up to go to my buddy's graduation and I will have 40 minutes in the car each way to talk to her, plus graduation and the after-party."

TL;DR- A girl seemed interested in me, I like her, we were talking really well for about 5 days, but she seems to be ignoring me now!

She seemed interested, yes? Here's the question: The past 2 days she takes forever to respond to texts, and I barely got 2 texts out of her today. She was working when I texted her, so I texted her again when her shift answered, but that was about an hour ago and she still hasn't answered. She is always saying that she's tired because she works a lot, so I don't know if that has anything to do with it. We were supposed to have a date this wednesday. Does her shyness play a part? Has she lost interest already? Up till now she had no problem talking me.

...or am I overreacting?