Baby Robo Hamster lethargy help?

i just got a baby robo hamster and the previous owner says she is like 3 months old but when i brought her home she became really lethargic. She was the smallest out of six and wanted to sleep a lot. A few hours later i got home and she wasnt moving but she was breathing. I dont know what to do, i think she might die... She is still tiny compared to her brothers and sisters, when i touch her she doesnt move and i can just move her and she seems dead. I cant go to a vet because of the cost and i just really need advice.