Hello, I'm Dr. Gregg and I will try to help you this evening. Sorry baby girl is sick. There are a number of things that could result in her illness but the important thing here is this bird is in trouble and needs the attention of a vet experienced with birds. These little birds do not tolerate illness and no food for long. First thing tomorrow I would call your vet and get this little girl seen.
In the longer term you need to improve baby girls diet. Seed and veggies is lacking all the good things a baby bird needs. Tou will want to switch her over to a good pelleted diet, such as Harrisons or roudybush.That should make up about 60% of the diet. Dark green and yellow veggies should make up the rest of it. An occasional treat of a few seeds or nuts is ok, but this is basically junk food for birds. Switching over to a good diet will take time and persistence but is worth the effort.
I would suggest you go online and find out as much info about birds as you can. The more you know the better off your birds will be. Yahoo has bird owner groups you can join. There is a website with a lot of good info about birds and most pet animals www veterinarypartner.com.
Good luck with baby girl and I hope she does well. If you have further questions feel free to ask. I'm here to help
She died this morning. I cleaned all the seed out and cage. Her brother is still fine. I give them raw veggies, no nuts but I use a good name brand food. I also give them hard boiled egg every day. They like brocolli