I'm not an expert on corns, but my 14 month old normal corn, Lili, eats 1 or 2 fuzzies (mice) per week. She seems fine with that, and is growing quickly. I don't know how normal her diet is, although we are following the instructions of her breeder, and it seems to correspond with what we've read. That seems to be significantly less food than yours is getting- maybe yours is just not hungry? Are you thawing the food too much (cooking it)? Is it too cold in her viv? When they slow down in cold weather, they can go without food for months.
These are the first questions that came to my mind. Hopefully they help, or someone with more experience will chime in, but it seems like it probably wouldn't be harmful to wait her out awhile, since they can go for so long without eating... Has anything changed since you posted?

Has your snake eaten since then? (I just looked here after not being on tribe much for a while.)

All my corn snakes brumate over the winter, except the ones less than a year old. (9 months isn't too bad - wondering how she could be that age, though - January is a strange time for a clutch to hatch!)
Brumating is like hibernating but the metabolism doesn't slow down quite as much, and it's what they'd do naturally - you can get more info elsewhere, but basically I reduce their heat when the light decreases (October or November, usually, over 2 - 4 weeks) and they won't eat again 'til I've warmed them up for spring. Yours might be reacting to light levels and getting that it's fall, and slowing down accordingly.

You can try setting up a light on a timer (12 hours on, 12 off) and making sure the heat is high enough if you want her to eat, or you could let her brumate if you make sure you have the right info on it. If she's too cold she won't be able to digest properly, so definitely go one way or the other. It sounds like she was eating very well before (rat pups are more caloric than similar size mice, fattier I think) so she could probably go quite a long time without eating.