Yes your plant will grow. it will prob flower early because under 7-8hrs it prob thinks its the fall season (unless its a special veriety). Mine flower in less then 13hrs.
If your GF gets worried about the setup then change the setup until she's onboard, your GF is your 1# partner in this and she should be included.
Dunno the factors involve besides the wattage, although a HPS lamp is an allaround favorite, some poeple like to alternate with HID lamps first, and HPS lamps later in the flowering/budding stage.
Anyway its been awhile since I did any indoor work, mostly an outdoor guy now. Indoor was fun, but trying to control every aspect of nature is tricky and you end up falling short. Good luck, keep me posted.