Yeah, you're right about the part that she isn't well-socialized, cause she isn't. It's not really a BIG problem, though, cause we got her to be a watch dog for our workshops, because our house is connected to my parents' and grandparents' workshops. So, I know what's in your mind. "Then why did you have to start this thread?!" Well, I started this thread because her behaviour is getting kind of annoying to me.
And you said not to scold her. Yeah, that's a good point, but the problem is, I already tried NOT scolding her before, but nothing changed. She just kept attacking our other dogs. When I DID scold her, her aggression lessened. I'm sorry, but I don't think she's scared. She's just overly dominant.
Our other dogs (three German Shepherds, a Dachshund, and another mongrel which is her son). She's like so aggressive towards our other dogs, even the German Shepherds! She just attacks them and acts like she's the alpha. Luckily, our German Shepherds don't fight back, but they're also getting annoyed by her. (one of our German Shepherds, Coffee, is the REAL alpha!) Doesn't she know that she's, like, half the size of the Shepherds? but she's not aggressive towards her son, she's just overly dominant, like Walnut (her son) is just inviting her to play, or he's playing with the other dogs, and when he comes back to her, she does that dominant thing, the one when she growls at him, holds her head up high, and puts her paws on his back. Oh yeah, and just so you know, Walnut is a young adult, not a pup.
So, back to my point. I think the reason Checkers (my dog) does that is because her brother, Graham, was being spoilt by their mother, Bubbles, and Graham was VERY bad tempered as an adolescent (and even until now, but we got rid of him). He just attacks Checkers for no reason, and when Checkers tries to fight back to defend herself, Bubbles comes and scolds Checkers by standing over her and snapping at her until she submits to Bubbles. Bubbles was really spoiling Graham, because even though Graham started the fight, she scolds only Checkers, not Graham. And even though Checkers didn't do anything, Bubbles just snaps at her and scolds her. Whereas when Graham does something unruly, Bubbles doesn't do anything. So does that explain Checkers's snappy behavior?
And, is Checkers really scared? Or is she just overly dominant towards dogs and other people? Are you sure it's fear aggression, because she wasn't snappy towards other dogs when she was an adolescent.
And, this extra information might help. I think Checkers's dad had a "bite gene", or "aggression gene", because all three of her siblings (including Graham) just attack people and really bite them, as in the teeth really come in contact with the skin. The reason I'm blaming their dad is because Bubbles is usually very good-tempered towards people and certain dogs.
All the other tips you gave are helpful though, so please don't take my arguments personally. I just want to tell you these things, so that you will fully understand, and you may have another solution.