HI I 'm dr Steve
Since she is app[raoching sexual maturity, she mayhave a vaginitis or metritis ( uterine infection).
Usually the cervix is closed and prevent infections of the uterus, but as a doeling comes into heat, the cervix opens to allwo semen in and this can also allow infection in.
SHe may be a little young for this, but it is a possibility. IN any event the green discharge is likely an infection and would possibly respond to antibiotics. I have had good results with using excenel. This is a broad spectrum antibiotic that is typically available from a vet. The advantage of getting it from a vet would be that he may be able to get you a small amount not an entire bottle.
If your doeling is not eating or is acting sick, then she should be seen by a vet to determine if IV antibiotics are more appropriate. I hope this has helped. If it has would you please click the submit button so I may receive credit for my answer. I will check later to see if you have more questions. THanks for using just answer and good luck.