Whether your supply goes up or not, you can still breastfeed your child. You may have to offer more supplement for her to thrive, though. If you can get domperidone, that may help you max out your supply, and fenugreek capsules (9-12/day is the usual) might help quickly. But any milk is good, even if you wind up having to supplement more to help your daughter grow and develop well.
I would not discount the ped's advice to get your child more to eat. My son was starving before we found out I had extremely low supply, but he still peed and pooped normally. (Thankfully we found the issue on day six, so he started gaining again.) Still, nursing is not hindering growth, so there's no need to end it just because your baby needs more formula as well.
Oh, and I read on an herbalist site that sipping water slowly fights dehydration better. A cup or more at a time triggers the bladder, so you don't keep as much, is what she said. Don't know if that's true, but thought I'd mention it.
Summer, wife to DH (07/99), SAHMama to DS (07/08) & DD (07/10).