Her Work Clothes

You actually made me wonder exactly what 'vanilla' was, so I ended up searching it up. I used to think vanilla meant romantic and loving sex, but apparently vanilla means normal consensual sex. That made me stop and think for a bit.
In speech, the tone and inclination of the voice can have a massive effect on the meaning of the words. The way she's hesitantly saying the words and how she's reacting really shows how she's not that against having sex. Make no mistake, if she was hard stop against sex, she would have reacted very differently to this scenario, so I think I can make the argument that this sex was in fact, consensual. Since the two of them are boyfriend/girlfriend, then turning lovers is a natural and normal progression, so I think this can be considered to be normal and consensual sex, therefore vanilla.