Jody, the play biting is just play and let them work it out between them. She will learn, trust me. It forms a very strong bond between the two of them, and teaches her doggie manners. I'll tell you right now when Maggie and Molly are going at it......it sounds like I have a major dog fight on my hands, but they're all out playing barking snarling biting pulling.....tails wagging. A few times I really thought Molly was losing her temper and I'd try to tone it down only to have her look at me like "hey mom, we're just playing, it's ok, can we still play some more?" LOL And it took some time but Maggie has learned when Molly doesn't want to play, then she just doesn't and to leave her be.
This is what Molly didn't get with Betsy because Betsy's Momma wouldn't allow it. Molly and Betsy were close, but nothing like Molly and Rowdy (who got to play that way). Molly and Rowdy have never ever had an argument between them. And eventually Betsy had to go to Nichole's because of jealousy issues (also cuz I'd kept her for Nichole though). IF they can really play together, they usually get really close relationship / bond wise.
Now when Molly doesn't want to play and Maggie still has a lot of energy, she'll bring me a toy to play with her instead. Rowdy, she's learning quickly does NOT play. He has all he can do to get up on his feet and walk. But he will allow puppy kisses and a little chewing for short periods.
Do the worming & then again in a month to make sure. Since you're in the trailer, worm the dogs every month because you've no idea of the animals roaming the area and whether they have worms or not. And worms make them hungry, worms are getting the nutrients.