I'm curious to know why you feel the need to wean completely just because you're going back to school. Many mamas balance work and breastfeeding, and I guess I don't understand why you couldn't balance school and breastfeeding. You wouldn't necessarily have to pump like working mamas of young babies do, but you could definitely still nurse your daughter when you're home... nights, weekends. Nursing while you're home would also reestablish your breastfeeding relationship and maybe help both you and your daughter with the transition.
As far as curbing the night nursing, the biggest thing triggering that, I believe, is that she's in your bed. She's close to the breast, she can smell you, and she knows what that equals. I would recommend getting her into her own bed before I would recommend you weaning completely.
With that being said, if you do decide to wean completely, be sure to do it gradually. Try for 1 feeding every 3-4 days to allow your breasts, body, and daughter the chance to equalize. If you do a sudden weaning, you run the risk of engorgement, plugged ducts, and hopefully not mastitis. You have to give your body time to catch up to the new supply and demand. Unfortunately, it sounds like your daughter just isn't ready emotionally to wean. In the long run, she'll be fine, but could you hold off weaning for a few months? Or do it more gradually and maybe eliminate 1 feeding every 1-2 weeks? Just a suggestion...
Whatever you decide, I applaud your decision to breastfeed your daughter this long!!! The benefits are ENDLESS :) Good luck with your family AND school!