I wouldn't hesitate to use a larger tent car camping. Bad weather that forces you into it, or when it's really buggy will make you glad for the space. I differentiate between what I carry in storage tubs and what I carry on my back. The propane two burner grill/ griddle weighs as much alone as what I normally carry on my back for a week. However, I usually don't have full blown bacon, egg and homefries for breakfast or grilled steaks on the trail. Having a good cooler is a luxury. Many times camping in state parks I feel more foolish with a tiny tent parked among the RV's and cabin tents. We use an expensive 4 person 4 season tent for car camping, but I can easily see going larger (especially taller) and probably will. The likelihood of getting your girlfriend to go is much better when comfort is achievable.
If she enjoys it and wants to get closer to nature, backpacking will be the next step. Some people cannot get use to sleeping on the ground, no matter how good the mattress. Cots will fit in that tent with ease. Have a great time!