Peter wasn't all that shocked by her reaction. This wasn't any easier on her than it was on him, and he knew that. She just wanted to keep up a front with him, for whatever reason. However, now, her walls were down.
For awhile, he just stood there, arms wrapped around her as she cried. He didn't care about the makeup on his shirt, didn't even think about it in the least, really. He just wanted to be there for her like she had been for him so far tonight.