Boy, that escalated quickly. I mean, that really got out of hand fast!
Anyway joke aside, in the rare case the author might be reading this (or a different author with a similar idea) add some build up scenes before going straight into vaginal fucking with creampie like this guy did, ex: there could have been party filler where this gets her progressively more excited as she consumes more and more drinks and the guy himself starts touching her in more daring places, especially once the boyfriend and other party members leave / pay less attention.