Take it slow with heeling and your girlfriend. I feel that the biggest fear is that they think the boat will turtle. My wife was that way until we put a rail in the water after an unexpected gust hit us. We rounded right up now she is fine with heeling. That's what mono hulls are supposed to do.
The other day on a friends boat my wife and his lady friend were down in the galley fixing a snack and we were heeling pretty good. They were having a blast.
Be easy with your girlfriend and let her learn at her paste.