When the word for the Christmas party came out, Hermione immediately thought to invite Ron since she didn't think that it would be prudent to ask Ginny to be her date. It had been something she'd wondered about for the past month. While she had enjoyed the snog and it had left her wanting more, Hermione didn't know for sure if it was supposed to be a one time thing or not so she simply acted as if it hadn't happened. Not to mention that she'd noticed Dean Thomas trying to talk to Ginny.
So here she was the date of Cormac McLaggen instead and having an absolutely miserable time. He was rough and handsy, not at all the type of gentleman Viktor had been at the Yule Ball or how she even imagined Ron might have been. She'd spent the night hiding from him because every time Hermione thought she got away he'd reappear behind her. Each time without asking he wrapped his arms around her from behind his hands fondling her breasts when he did.
Each time he came up to her she feigned interest but it was getting old very quickly. Her eyes traveled often to Ginny who was looking much better in her dress than Hermione thought she did in her pink v-neck cocktail dress. Finally, Hermione had enough and rather than make an early exit, she took up refuge behind one of the curtains along the wall of the office where she figured she would wait the party out in solitude.