I agree it's a thin line. I'm kind of a softie myself when it comes to lovebites. my angel gave me love bites all the time and I loved it. I could definitely tell with her if it was a MAD bite, though. it was pretty obvious because it was always my fault - you know, trying to clip her claws or something or when I was just learning how to do subQ fluids and poked her with the needle.
I am currently fostering a 2 year old cat rescued from a hoarding situation and I'm also trying to "teach" him not to bite OR scratch actually. 2 weeks is not very long still for you, so I think with your little girl it will just take time. it sounds like she's a smart girl and is already learning. I've had my foster for about a week and a half and progress is very off and on, but I feel he is learning a bit, too. I do the same thing. i play with him with toys a lot to diffuse his energy and when he bites or scratches, I say NO and then leave the room. there have been a few times for him as well when he ALMOST bit, but didn't once he saw it was my hand he was about to bite. and even when he still swats at me occasionally, he does not have his claws out at least. I think that's a good sign. overall he has also really warmed up and lets me pet him a bunch and will even jump up on the couch with me, but he's still a little skittish and I think easily overstimulated.
my advice is just to keep doing what you're doing and know it might take a little while for her to fully learn. that seems to be the recommended way to teach cats not to bite at least. of course, i'll be lurking here to see if anyone else has other advice! cuz I would find it helpful too!
Kitty, Lucy, and my sweet Angel forever in my heart.