Nursing for shorter time when milk really comes in?
I would be encouraging her to eat as much as possible personally. Trying to keep her awake and nursing longer. When she starts to drift off switch sides and try to get her to latch again. Do breast compressions to get her a jet of milk and hopefully wake her up and get her drinking again. I'd also be offering her the breast pretty much any time she even thought about getting restless or showing any kind of hunger cues. (sucking motions, hand in mouth, rooting etc.)
Are you still pumping and supplementing with a bottle?