'morning, GypsyGSD! I had the same problem in reverse. My border collie is the younger one & when we got him, we had 2 gsds. Jake used to play with them, but got quite rough sometimes & if I told him off, the male shepherd would have a go at him, too, although the bitch was quite tolerant. Now that we no longer have the old fella, Jake has calmed down, but still plays rough (poor gsd's now 8 yrs old) & she gets really fed up with him. If they start, I tell them both off & it works, although it's not her fault, but his. (you should see the look I get from her!) Maybe your collie is still getting used to the fact that there's a "baby" in the house - she's not jealous, is she? You say she's highly strung, so maybe she feels a bit confused & also thinks she's backing you up when you admonish puppy. I'd keep an eye on her though, in case she goes too far. Do they play together in the garden ok?