I think little Chowder is just lucky that such a responsible person took her home, and was able to take the actions to make sure she was healthy and well cared for! You should be proud for reacting well, and glad that you were the one to take her home. I hope she's doing well with her foster mommy, and that she'll be back with you soon!
For comparisons sake, my Sophie was actually about six weeks old when I got her (she was weened early, also by a foster mom, according to my breeder), and she looks much older than your baby! The picture of her in my profile is from the day I took her home.