I think it's not uncommon for female dogs to have issues with one another in some situations...especially when maturing? How long have they all 3 lived together?

You may also want to have them all checked at the vet - any odd behavior changes without explanation I'd make a vet appt.

 

We’ve had the mix for about a year and not had any issues for the most part. If I can just keep them apart for a while and it’ll go away I can live with that. Just don’t want to get any of them snipped if it isn’t going to help here.

 

That's going to be a discussion to be had with your vet. Crate/rotate can work for some people, but I'm not sure there's enough info here to know whether or not you may have to do that forever. And it's worth discussing the potential behavioral changes that could happen with a spay as well as other health issues that may occur with a spay vs. no spay. I understand wanting to wait for a spay later in some dog breeds, but as far as I know (I do not have a female dog, and our dog is an adopted one that was neutered when we got him) the risk of pyometra in unspayed female female dogs is ~25% by ~10 years old, which is something to discuss with the vet as well.

Are you able to find and do some sort of consultation (in person or virtual) with a trainer specializing in female dog behavior? To just assess what the issue might be and what steps you might be able to take? That's where I'd start - but first I'd keep them separated until I figured something out.