Well, you could try feeding raw ground meat. If it's supermarket meat, then you'd have to add an appropriate amount of calcium. Plus if she gets picky, you could barely cook the food, or cook it less and less until she's on raw (that's what I did when I transitioned Bailey). If you can get raw w/ground bones, like from a co-op, that would work, too. Obviously, you wouldn't cook anything with bone.
It's a bummer that she doesn't like RMBs so far, though. That's Bailey's favorite part! Have you tried a variety of RMBs? Maybe duck or pork necks would work? Or lamb breast (ribs), those are pretty small. (Hopefully someone like Dekka will chime in as to what smaller dogs eat for RMBs if I'm mistaken.) I'm sure Mia would be happy to eat whatever Summer rejects.
It took Bailey a bit to get the hang of it. I had to hold the duck necks for him at first, lol.