gameoldbird I thoroughly refute the suggestion that one breed is better than another or that a GSD - and I have 2 currently, not my first GSDs, and have fostered them too, plus I work with several - is any less a "gentle breed" than any other.
I also resent the idea that an assessed, well matched rescue dog is any greater risk to a family or DC than a pup (which as it grows could turn into any type of dog, there are no guarantees, with an older dog character is established) - particularly from a "family home breeder" (which generally means BACKYARD breeder IMHO). I say that as a rescuer with some considerable experience.
Now I've said that I'll leave it to others to make suggestions wrt training, that's not my area.
I will say this to Bean, in response to her DH's comments: ". Its at the stage where my OH has started going on about having her put down, due to the risk to DD, the fact that she wouldn't be rehomed, and a serious skin disease she has that causes her to bite and scratch herself until she bleeds."
I work with rescues which would not dream of killing or suggesting that YOU kill your dog, even if you were unable to resolve your concerns and even if she wasn't able to be rehomed (which I doubt very much to be accurate anyway, in fact I'd bet my last dollar that it's not).
I ONLY work with no kill rescues and those which will offer dogs sanctuary for life if they need it. Should YOU need it - though I don't for one moment think you will if the situation wrt your dog and DC is properly managed (think dog is warning, IMHO, btw, and not jealous, just concerned) - then I will do my utmost to find your dog that help... PLEASE don't even consider killing her and PLEASE NEVER, EVER rehome privately (see recent other threads on here for reasons why not) but intead approach reputable rescue.