A clean room is the only way to prevent spider mites. Around here, pretty much impossible.
The little demons will ride in on you, your dog, or that bag of potting soil.
For now, pull each plant out, and with the aid of a magnifier, find them and kill them. In this situation, I wipe off the webs and mites by hand, daily, until harvest.
If you have the cash, start using beneficial insects in your room. Most are very tiny, and unlikely to freak your girlfriend, but they really do the trick in enclosed spaces.
This outfit carries an excellent selection of predators.
http://www.arbico-organics.com/category/beneficial-insects-organisms
I've had excellent results in my greenhouses, using these critters.
Regular ladybugs are cheap and effective, but tend to wander away, fairly quickly.
If you have at least three weeks until harvest, I'd consider getting the Ladybugs, after you've removed all you can, by hand.
Sorry for the bad image. Can't figure out how to delete it...