Even if he does proposes and it were for real, it's not going to be a surprise anymore. His gf might even feel it's done only because she practically pushed him into a wall with that and both will probably end up resenting each other. I have a feeling their relationship will not last for too long. The OP's gf doesn't sound willing to wait for another year and he is going to get more pressured into it.
I would very much hate a man proposing because of me and not out of free will; because he wants to.