M.S.
Just an FYI--those who suggested pumping didn't say how much. Don't pump until your breasts are empty--then your body is being told to make the same amount. You're probably nursing your daughter right before bedtime and so at that point you're empty. Maybe when you wake up soaked, pump for just a few minutes on each side to relieve the pressure (you can even hand-express into the sink to avoid dealing with getting the pump out in the middle of the night) and then in a couple of weeks you should be fine.
By the way, I am super jealous--my 15 month old is seriously just now starting to sleep 11 hours at night. You are a lucky, lucky mom.