Something occured where a firmer hand became necessary.  End of story. Snapping and snarling and biting humans out of anger/annoyance is never, ever, ever ok - even if you're a 6 week old.
Things have become much calmer, happier, and more aligned entirely around here since taking control of that situation and that was literally the only mandatory thing.  Dog is much more respectful, and seems oddly happier, than she has been since she arrived.  Her trainer was 100% right.  It's not like I'm doing this without onsite professional consultation and assessment.
A 6 month old is a puppy.  At any rate, as I mentioned, she will not be shocked or harmed in any way with a Halo collar, and no real aversion training is planned.  I do not have an "e-collar" for training, I want her to be able to run her property free, off leash and stay away from the main road.  We will practice for months and months on leash if that's what's required, but she'll get used to the tone and learn what it means.  It's legitimately no different than me training her to recall with a whistle, except I don't actually have to be watching her once she learns it.