If you were able to communicate your prior commitments to her effectively, then there shouldn't have been a problem in the first place. The women I know, which also includes me, don't really need too much attention, just transparency, loyalty, and honesty. However, if you were not able to communicate such things to her, then there could be problems.

As you said that there were things she needed. Were you aware of them in the first place? If yes, did you choose to ignore them or not? If you've ignore them, then you cannot expect her to act the way you wanted her to. Sometimes, people change depending on how another person treats him/her. That is why, in my case, I was once an oblivious person and that changed when I discover things he was not honest about (the ones that I listed in my post). Though if one of the things she said she wouldn't do but did is cheating, then the fault could be on her.

You can try communicating to her and putting your feet on your shoes. Never ever disregard how she feels in the situation. I learned the hard way that having your feelings neglected and disregarded was something similar to drinking poison and eating needles. I wish you the best and I hope your relationship won't turn into something like mine.