My son was a real crab from about 4 months until about 5 months. He was an absolute monster for about 2 weeks of that, and gradually went back to his happy little self over the next 2 weeks. 4 months is very commonly a tough time to be a little baby. I think at least a small part of it is that they are becoming much more alert and don't quite know what to do with themselves.
However, this was only one night. Maybe she had a tummy ache, or a headache, or something like that and was just unhappy about it. We all have nights like that. She may be perfectly fine tomorrow.
Try not to stress yourself out too much about these things. Whether it was one bad night or the start of an unpleasant phase, it will pass and all you can do is try to comfort her through it.
K. Sophia - Mama to my little lactivore, the amazing Mr. X (11/10).