OK, thanks - here is what I would do with this....
Start on a weekend when you have some time to spend with the dogs and make sure everyone in the house knows, understands and does the same things as you. Start from the minute you get up in the morning.
From this moment on no shows of dominance are allowed between the dogs - if one shows any dominance it is told, "No!" very firmly and told to lie on it's bed for five minutes.
From now on the dogs have to sit before going outside, you open the door and say one dog's name and give it a signal to go out the door. The other dog has to remain sitting until you say it's name. Do this as often as you can as it will take a few goes before they are used to it. Swap which dog goes first as much as possible.
When going for a walk get the dogs to sit quietly and swap which dog has their lead put on first.
Practice going out and leaving both dogs loose, leave them for three minutes to begin with (start to stretch this out when you feel in complete control of the situation)and insist that they both sit before you say hello when you come back in. Again, swap which one you greet first (do this very calmly - just a calm stroke each and then tell them to go to their beds. Once you are in and put the keys away etc. make sure you take them out and play for a few minutes).
Almost every thing can be done in the same calm way making sure they take turns at being first - the idea being that you are the alpha and will not tolerate dominant behaviour between the dogs with less status in your pack. By keeping the situation calm and controlled when you come in you take away the frenzy of excitement and the need for a show of dominance but the dogs know they have a play session coming to let out their excitement.
By the end of the weekend you should be feeling a lot more comfortable with leaving both dogs loose and they should be more secure in their standing with each other.
Let us know how it goes - it's best to nip two bitches having a go at each other in the bud as soon as possible, but some just do not get on. I don't think this will be the case with yours as the biting was only in one situation. Good luck.