Oh my goodness, I am so sorry to hear the bad news
When my best friend bought her Yorkie in April, she too had Parvo, and she too was almost 4 months old. Her puppy DID come to her with Parvo (she bought her from a very, very NASTY lady, unfortunately she did not know she was like this in the beginning) and our vet did not think her baby was going to make it (she had some highs, and she had ALOT of VERY BAD LOWS...), but after being in at the vet for 2 weeks, she came out just fine! Granted it messed up her coat and it is now very thin and coarse from being sick, but the important thing is that her baby is alive and well.
I will keep your little sweetie in my thoughts and Prayers. Please keep us update on how she is doing!