Actually your older dog is doing everything right.

Actually your older dog is doing everything right. She's not beating up on the puppy, she plays with it when she feels like it, and she's warning it when she doesn't want to play and not fighting with it or trying to hurt it. She may be avoiding it indoors just because she doesn't want to play. She sounds like she's being really tolerant of the interloper, but just keep a close eye on them for a while. The pup will figure it out sooner or later.