Is she really alpha, or could she be fearful? That will make a difference... She may simply dislike another dog sniffing her without her acceptance - herding dogs can have persnickety social rules that they're not shy about enforcing. Was she socialized with other dogs as a young dog? How does she treat very young pups? Very young - 8-12 weeks? You don't have to answer these questions - they're really just things I'd consider as I contemplated how to go about this. For most of my life I've had what some would consider a "pack" of dogs - as many as four, so not really a pack though. Depends on who you are... Among these I've had 3 intense herding dogs - a Belgian sheepdog, and 2 English shepherds - all males. Only one of them has had difficulty accepting a new dog into the pack, and he is truly alpha. An extreme rule-forcer, very obedient with family, smart and intense. Both dogs he's had issues with have been males, one neutered, one intact. At this point I have him (intact) and my youngest intact male (whom he doesn't care for), and another spayed female who's easy. It is only his reliable obedience that make this at all doable for me. If I weren't so comfortable with dogs, if I didn't really love them, if I was uncomfortable with occasional dog fights (never any serious injuries at this point, because my youngest, Huck, always backs down immediately), this wouldn't work. I spoke to some pretty dog-savvy people before I got this youngest dog, so I knew what could happen, and how to lessen conflict, and this is what I learned: you have a spayed female - so you really should get a male puppy - very young. DO NOT get a female - females together fight more than any other combination. Look for a middle-of-the-road pup. Work with the breeder to make sure they understand why this is important. Make sure your girl is obedient to you without question. Brush up on this A LOT before you bring that pup home. Have her practice "submissive" things - letting you go through doorways first, laying down before getting her good, sitting for treats/petting, "going away" from you when told, sleeping on the floor instead of your bed, not getting on furniture... Are you familiar with resource guarding? Obedience will help you curb that a bit. And you might want to crate train her, if she's not already. She might need/want a place to retreat to when the pup is bugging her. Personally, I'd go for it...