They are probably doing this at your house because her parents make it to hard to do at hers. Just because they can, doesn't mean they should. And doesn't mean that any set of parents needs to make it easy for them. If they want to, they should do what the rest of us did. Sneak around in cars and places where it's not all that comfortable
Or wait till parents aren't home. Nothing breaks the mood faster than seeing the headlights of the parental car in the driveway.