Why is she not returning my calls?

Alright, so I've known this girl, let's call her Sarah, for a few months. We met in grad school and had a few classes together. Long story short, we got along well and became friends, but I never made it clear that I had feelings for her.

So, I finally asked her out last Wednesday (2/10), and she said yes. I told her that I wanted to go out with her on a date to get to know her better. I also said that I enjoyed spending time with her, to which she said that she felt the same way. We spoke again that Friday, and I asked her to be my Valentine, to which she said yes also. But she had to work that V-Day, and it was Chinese New Year, so I was going to spend the day with family anyway. Plus, I didn't have a car and was getting one in a few days, which I told her.

I call her on Tuesday and she doesn't call back. I call her on Wednesday (last night) and left a message and she didn't call back either. I finally got my car last night, and I'm ready to take her out on a real date, but it seems that she's ignoring me. What the heck did I do?

Should I trying call her again? Or maybe text her, if for some reason she doesn't want to talk? I would really like to take her out, don't want to seem like I'm desperate by calling everyday. But geez, I'm starting to think about just letting this go.

You contacted her enough times to state your position.

Its better to not focus on the reason why but the fact that she is not responding. Her reasons are her perogative. If she wants to go out, she will respond. Give her space.

You put your offer on the table--not all fish are gonna bite.

Do you have another way of contacting her? I know it's a long shot, but she might have lost her phone or something. If not, she's being incredibly rude, but give her the benefit of the doubt and try to get in touch another way.

Well, I ended up texting her that evening just to ask her if everything was okay. She replied that everything was okay, and that she was busy with work and would give me a call later. Guess what? She didn't call and we haven't communicated since then.

I really liked her, but I'll just have to let this go for now. People have the right to change their minds, but I'd just like to hear straight from her what happened. I'm perplexed more than I am sad or upset.

IMO, let it go. I'm in a situation that has some similarities, with the door open for communication from her after giving her the specific method to do so (at some risk to me) and it's been about five days so far.

Overall though, I'd say once was enough to contact her expecting a response. Besides the fact that it looks needy, in my opinion if she really cared she would have contacted you with a bit more of an explanation. Normal people make the time for the people they care about...