If you stay at North Lake, Carnelian Bay is pretty far away from everything, but "Everything" is a relative term on the North Shore. There a few good restaurants, LOTS of good mountains...that said, one that everyone leaves out is Mt. Rose. It's on the mountain road from Reno. Highest base elevation of any mountain out there, so if you're not sure about altitude sickness, not the best place to start. Also, being on the middle of the mountain, there is absolutely nothing to do there if your girl isn't riding, but on Wednesdays they have 2-for-1 lift tickets, and the diamonds down the front are great for some serious charging. It has two main lodges on opposite sides of the mountain, one with a big-ass deck for enjoying a cocktail, especially on a warm Tahoe day. Great vibe, there will lots of people lounging around in tank tops on the deck. And while the views are great from up top, the peak is not only high, but tiny. It might kind of freak you out when you first get off the lift, because it drops right off. It can be a weird experience at first, but once you're used to it and know where you're going, I think Mt. Rose is a lot of fun and highly underrated. As is Homewood, also in North Lake. Homewood is super quite, only two green trails whose only real purpose is to return you to the two base lodges, otherwise it's all blues, blacks and glades -- and the most beautiful views you'll find on Tahoe. Some trails you can't even see the bottom, you just feel like you're going to ride right into that beautiful lake.
That said, the others' advice for your girl isn't bad. Personally, I can't stand Northstar, except for the long-long black trails running down the opposite side. Otherwise it is just a huge shopping mall with ski trails. Again, though, it will give your girl something to do while you ride. Mostly blues, mostly short, and the parking situation is terrible, even if you get there early.
Even if you stay at North Lake, the drive to South Lake is easy, beautiful, and scary as shit in places. The trip around Emerald Bay is not to be missed...just leave Heavenly or Kirkwood in time to kit the sunset and get home before dark. It is NOT a road you want to be driving after dark. If it's snowing at all, they'll close it in a heartbeat, too, but you can always drive up the other side of the lake, which is a much bigger road, still pretty, just longer.