How old is Pedro?
Its very normal for adult dogs to correct puppies by growling and snapping. The puppy should take cues from this and start learning how to behave around Pedro. Does she back off when she's growled at? If she doesn't, you may have a problem on your hands.
Just let Pedro correct her (as long as thats all he's doing - growling and snapping). If you stop him from doing this, he will have no way of warning her then just go straight for the bite!
Oh yeah, and its important to give them breaks from each other because puppies can be so annoying to older dogs. I would suggest getting a crate for the pup if you don't already have one.
Shiloh, Reece, Lolly, Skylar
and fosters Snickers, Missy, Magic, Merlin, Maya