Advice on 3-month-old lhasa apso/poodle mix behavior
I just got a lhasa apso/poodle mix (aka lhasapoo) 4 days ago. I am experienced with dogs and puppies, but this is my first small breed puppy. She is 12 weeks old. When I picked her up she was sweet, sweet coming home in the car, not even a whimper; seemed completely adjustable. Doing AWESOME at potty training. She loves everybody usually, my kids, lets them hold her, licks them acts like a cute little puppy. I did lots of research before I got her, just as I have just spent lots of time researching her issue, ha. I mostly found the mixed breed overall is very affectionate, great family dog, loving, good with kids and cats but of course had to be socialized with people and other dogs, and good training to avoid small dog syndrome - no brainer, right? I did find the occasional opinion in a forum and even some websites conflicting that lhaso apsos are not good with children. Anyway, she started growling - growling at my other dog (a 9-month-old great pyrenees, so MUCH bigger than her), growing at us even. She growls at the dog when it passes by her crate, she growls at any of us if we "bother" her sometimes. Sometimes her growls turn into full-on snaps and bites/attacks. Obviously, it's painless for the most part, she isn't even a pound I don't think, but this HAS TO BE CORRECTED NOW. I think it is important to say she either loves everybody (including trying to play with the other dog) or she growls/snaps at everybody (including the dog), meaning I don't think it's a kid thing as she does it to even me.
She is crate trained/ing.
I thought maybe she is just transitioning still? Is it possible my house is too "loud" for her? Could it be fear aggression? Does it sound like something she will grow out of/we can correct? She's a baby for goodness sakes and when she is running around she is a happy-go-lucky puppy and so adorable. So then I thought, no she is testing and trying to be alpha female. It did dawn on me to quit thinking about it and just treat her like any of my other dogs and same rules regardless of her dainty size - that's how they get their reputation. I have always been against it and I fell right into the same shoes in a day, carrying her around and realized wait this is a dog with 4 legs. So maybe overstimulated?? I have tried holding her mouth and other little corrective actions, but they make her react worse/meaner in the moment. So my question is what is the best way to stop this/nip it in the bud right now?