I only foster small dogs, but I have four of my own, so my new fosters are coming into an established pack. Here are some things that have helped me. I spray all my dogs with the same scent before I introduce them. If possible, I start the introduction in as neutral and area as possible, one dog at a time. I try to take them for a walk early on in the intro. Start your foster out in a cage (wire if possible so she can see what is going on around her). As to how you treat her, that depends on the personality of the dog. Try to remember that depending on what her past is, she may have certain illogical fears. It seems to take an average of two weeks before a dogs true personality begins to show through, so don’t judge her by her initial behaviors. Be patient and loving. I agree, have plenty of treats, but also be aware that depending on her background, she may not take them from you or even know what they are.