I know somewhat how you feel, but my situation is switched around a bit! Zoey is older by 2 months and beats the crud out of Dolly! She steps on her, bites her, pulls on her skin, pulls her tail, barks at her, and just bugs her to death! And she does not stop. I usually don't interfere unless the growling starts to sound like fighting not just rough housing. But I guess I don't interfere because Dolly is like 30 pounds heavier than Zoey and taller and she can fight back if she wants to. But she doesn't because Zoey is alpha and older and so annoying! Should I be interfering with their rough housing? I mean, I'd be outside every hour if so!