The reality is that she is 2 and she is doing a lot of growing and changing very quickly. Even for a very smart girl this is a very frustrating and confusing time. There is a reason they call it the terrible two's. She is still very young but is learning to establish control and independence, so it is very upsetting for her when things are out of her control.
One of the posters suggested saying how she feels. This is good advice, it acknowledges that she is upset and frustrated and it helps to get her back to the thinking part of her brain rather than the emotion part of her brain. Someone suggested putting her in time out every time she cries, but if you do that you are not acknowledging her frustrations and you are punishing her for something she really can't help. As the last poster said, you would force her to internalize her feelings, and treat her as if her feelings are not as important as yours are. That method may succeed in gaining compliance when you want her to stop crying, but it is harsh and does nothing to teach her how to deal with her own emotions.
I think the best thing you can do is acknowledge her frustrations, then nicely ask her to use her words then you can talk to her, then talk to her to try to find out what's bugging her, one simple question at a time. If you have been trying to get to the bottom of things for a while and still have gotten nowhere, or she still hasn't calmed down at all then you may just need to let it go. Tell her that when she is ready to talk, you will be there, but as long as she will not talk, you will not be able to help her. Asking her to use her words when she wants something is to try to get her out of her emotional state, and get her thinking. Even adults fail to think very well or function properly when they are functioning in the emotional part of their brain. That's why we tend to fly off the handle, or start yelling when the kids get very out of hand or we've had a bad day that just gets worse. So, if being an emotional mess is hard for us just think about how hard it is for a little toddler that hasn't learned how to work through problems.
She's only two. She will slowly learn how to work through problems, calm down when she's emotional, and communicate when she's upset, but that takes time, a long time. The best you can do is try to work with her, try to understand her feelings, and sometimes just try not to let it bug you too much. Two year olds are going to cry, and they are going to do it a lot. They will do many things that bug you a lot. So you have to choose your battles and let some of the little stuff go. Just remember that old saying, "This too shall pass."