Need your advice!She doesn't respond to my messages and call

Let me first give you a quick background. I am working for a bank. Over the summer we were working with two law firms on some legal stuff. There was this girl who had recently started working in one of those firms and was assigned to work with me on the project. I found her quite attractive from the very beginning and I was positive that I will eventually ask her out. Since we were working together, though, I didn't do anything until recently when the project was pretty much over.
Like a month ago, I called her up and asked her out. She was on vacation. But she told me that she would like to do that. When she came back to Austin, I set up the time and took her out. The first date went awesome. She actually told me that she is interested to go out again, and I could tell that she was excited about it. We decided to do something for the weekend after. In between, we were sending each other messages. Since we both are very busy, we did not talk on the phone much. The next weekend, we went out again. It went great. We went for a college basketball game, had dinner and even talked about some serious issues. She told me (and this is important) that she just came out of a serious relationship (which from what I have heard ended more than a year ago) and she has just started working at this firm, but she still would like this to become more serious. She then added that this won't happen any soon and it takes some time. She even said that I should not push her into this. After the second date, we still kept in touch via messages. Everything was pretty normal. She told me that she would like to go out again the weekend after (which is two weekends ago), but then she canceled on me the last minute, saying that she's got a lot of work to do (which I totally understand) and a high school friend of her is visiting the weekend after (which is last weekend). She also mentioned that we should do something else early next week (which is last week). I responded positively.
What is kind of awkward, though, is that she suddenly stopped responding to my messages after that last message. I even called her up last night and left a message. She did not call me back. This has been very frustrating for me, specially because I do know that she's got my messages. There is no way that she hasn't got my messages.
At this point, I don't know what to do. On the one hand, I really like her and I am willing to do what it takes to be with her. On the other hand, I do not know if she is still interested or not. I have no way to confirm this either, simply because she doesn't respond to my messages or phone call. I also don't want to keep sending her messages or keep calling her, because then I will come off clingy and needy. Over the last week, I send her three messages and called her once last night. I also don't want to push her. But then I'm afraid that if I kick back and do nothing, she may think that I have lost interest after she stopped responding. This communication break-down is killing me.

Do you guys have any advice?

Remember this;
'No Response Is A Response'
I think this girl is not interested, time to move on.
Sorry osborne.

Thanks, Yorkshirelass.
You would understand that this is quite hard for me to accept this and move on. I have to wait and see. But I totally get what you're saying.

You've done what YOU can do and you're right, if you do any more, you'll sound clingy and needy. Probably best to let her make the next move. She knows your there and if she wants you, she'll let YOU know. If she doesn't, then that is your answer.

-- Wed Sep 25, 2013 5:21 pm --

You've done what YOU can do and you're right, if you do any more, you'll sound clingy and needy. Probably best to let her make the next move. She knows your there and if she wants you, she'll let YOU know. If she doesn't, then that is your answer.

I would wait a few weeks and then if you haven't heard, send her a text asking her how she is and that you haven't heard from her. Tell her that you really enjoyed her company and that you would like to see her again and would like to know if she is still interested. Say you understand she is really busy, but you are more than happy to go at her pace and fit around her, but you would just be grateful if she would let you know how she feels and if she would like to see you again. If she doesn't respond to that I would just leave it.

You never slept with her (well it doesn't sound like you did) so no deeper foundation other than a couple of dates.

Thank you for your help, guys. I truly appreciate it.
She actually did contact me. She is apparently very busy. She sounded like she still is interested in going out with me. I responded back, saying that I would love to see her again. Now she is supposed to tell me when she would be free, so we can schedule something. It's been a while though. It's a wait-and-see situation, I suppose.
I don't know, guys. I'd love to keep seeing her, but I am not sure if she's as interested in this as I am. I simply have no way to tell. You might say (as Yorkshirelass did) that this malfunction in communication is, in fact, intentional and it is a sign. I do realize that this is a possibility. But what if she is really busy. I know her type of job (as I am sure you do), and some times they are really busy. At the same time, however, the mutual interest may die down since we don't get to see each other.
To respond to what theSarayiahpost said, I would like to add that I also would love to know how she feels about this. I just don't know how to figure this out. She already had told me that, although slowly, she would like to work on this with me. This is a very good sign. But then I don't know how to interpret this constant communication break-down.

This whole situation is new to me, and I am just lost!

I would suggest starting to go out with other girls or friends and trying to move on with your life. Continue to do your normal weekend activities from before she came along and don't put your life on hold because she "may not be busy this weekend"

I had the same thing recently with a guy I really liked and fell in love with but I told him I was not ready for a sexual relationship and then suddenly he stopped answering my messages. I tried to make excuses for him like "Maybe his cellphone broke or got stolen" and after I checked that my messages got delivered "Maybe he is really busy"... But the truth is always: If a person really likes you they would answer the damned phone even if they were in the bath and the phone is on the other side of a very long hallway! If someone really likes you but they ran out of airtime they will run (not walk, RUN) to the nearest cafe to buy airtime to phone or message you back.

It is hard to hear, I know but the truth you and I must both face is: "He (or in your case she) is just not that into me!"

Sorry if it sounds harsh but it is the truth...

Thank you, Thexena, for your advice. This is, in fact, what I am most afraid of.

I know. And it is a devastating feeling. I really do know that fear and loss you feel when you are rejected in such a silly way. I think this age of technology has desensitized people. It is so easy to just ignore someone. I am unsure who said this but I often think about the truth of this poem:

"Sticks and stones are hard on bones -
aimed with angry art.
Words can sting like anything
but Silence breaks the heart."

Stay strong. You will find someone someday that cannot wait to be with you. Someone who will find any small excuse to see you.

Thank you for the support, Thexena. I mean it. It helps.
By the way, that piece is by Phyllis McGinley. I adore her poems. But I never thought that this would apply to me someday.