Thank Goodness your husband was caring enough to pick this little girl up and I'm sure saved her life! God bless you for taking the time to give her a bath and showing her some love.
I know if I were in your situation, I would have a very hard time handing this little girl back to the owners knowing she's been obviously neglected.
I'm sure this little girl feels much better today and probably shows it!
I would definitely say something to them about her teeth, and the pain they have to be causing her, along with the suffering she's enduring with the fleas!
If its a situation where they can not afford to take care of this poor baby, maybe you could suggest a rescue center or if possible let you keep her.
Again, God Bless you and your husband for caring. I'm praying the owners will do what's best for this precious little girl.