If it's not any better by now, it's time for a visit to the emergency vet, angelajs86. Hives are always best treated as an emergency since they signal a severe allergic reaction. If you notice she's having difficulty breathing or she becomes very lethargic, you've got an emergency situation.
If she's holding her own, you can try to up the benadryl dose a bit. Our 55-pound males sometimes need 75 mg of Benadryl three times a day to get an allergic reaction in check. If you're uncertain of the dose for your dog, calling your vet or an e-vet should confirm how much you can safely give.
Good luck with your dog!
Keep us posted on how she's doing!