dog interaction

Question
I adopted an 18 month old full bred boxer named Bella from my friends cousin, shes a very active puppy and gets along well with humans. My cousin has a 13 month Black lab named Riley, both dogs are female. We tried socalizing them together last week and I thought it went well until rileys "daddy" didnt like that bella was nipping and growling, I noticed that both dogs tales were held high and wagging very fast. They left abruptly and bella was cryng and trying to break free from my grip because she as far as I can see play. Were these the right signs to look for from 1st time interaction between strange dogs?

Answer
Without actually seeing what the dogs were doing it is hard to say what the dogs' intent was. There can be a very fine line in reading dog behavior. Was Bella actually nipping (snapping???) or was she just mouthing? A huge difference. The high wagging tails could be simply excitement, or a sign of a dominant dog strutting its stuff and challenging the other dog.

When dogs play, they can get very rough. They leap, they tumble, they roll around and just wrestle. They mouth each other, and make horribly loud sounds that sound like they are killing each other. If the two dogs were doing that, they were probably enjoying each other's company very much.