
It would seem very young, but my worry would be Pyometra. does it ahve an offfensice smeell? If it is just a pale greenish mucous and she is licking then it could be cystitis or vagiitis.
The latter quite common in prepubescent bitches ans seems to self reslve after their first season, though may need antibiotics if troublesome, but it genrally returns until the bitches have their season.