
Be sure you don't allow Poppy to feel that the new puppy is more important than her, or you
will have major problems of resentment. Make sure Poppy has plenty of opportunity to get away from what she sees as an interloper on her territory, before she decides the pup's outstayed her welcome and can go home now! Poppy was there first, and needs to have her position boosted. Never leave them unattended and make sure Rosie has plenty of time away from Poppy when you can give Poppy your undivided attention, as she's used to.
Lots of older dogs (especially males, but not exclusively) don't really like pups very much, and who can blame them - we don't like being chewed with those sharp teeth either!

It can take several weeks for a new pup to be accepted, and until then the resident dog usually does his or her best to put the pup in its rightful place - at the bottom of the pecking order. As long as you keep an eye out so that Poppy doesn't feel compelled to get serious then I'd allow her to keep Rosie lower-ranking, in the way normal adult dogs do to upstarts! If you think Poppy's getting too rough, stop the game, put Rosie in her crate or playpen and take Poppy for a walk.
Your task is to support Poppy, which usually goes against our own feelings of 'poor puppy, it's a sweet little baby'. To Poppy Rosie's a nasty noisy sharp little thing that's turned her happy life upside down - don't you turn on her as well! ;) Scolding her for normal canine behaviour isn't wise. Good luck!