First off, that guy who threw mama and her babies out in the cold should be shot.
Is there anyway you can get a hold of the ex-girlfriend to let her know what was done to her cats?

Secondly, you are such an angel for taking in this precious little one. Seems to me like you are doing everything you can for her right now. Poor little thing. It just breaks my heart knowing they are out in the cold like that. AARRRGGG some people make me sooooo mad.
Plus, you are doing the right thing by keeping her separate from your other cats as they are your first priority.
Any chance in getting the other kitties and trying to find homes for them?

I wish you all the best and please keep us posted on the outcome at the vet.
Have you decided on a name for her yet? Also, give your hubby a hug for me, for helping these little ones by bringing them food.