Is there a way you could provide the dogs with a guaranteed safe (as in toddler-free) place where they can retire and where she cannot (or can be taught not to) follow?
What's really good about that sort of concept is that it gives your dogs an alternative. Like anyone else, dogs do have tolerance limits - and one day when somebody isn't feeling too well, and cannot get respite, well, a warning nip may end up being issued. Which would be entirely fair enough, of course. But still better that the dog has an alternative, such as a place to retire where the rule is "nobody bothers Layla/Gunner when she/he is xxxx".
I realise that still leaves you with the toddler to train

and she's not going to "get" that she's not allowed to bother the dogs when they go to their bed (or wherever their "safe place" is) instantly. But it's still a good idea. And it can give you the opportunity to stop her from approaching them there, rather than stopping her from biting (meaning one step earlier in that progression). Worth a thought, anyway.