If you've been keeping rosies that long I will assume you have a feel for their behavior in captivity, as in the seasonal fasting that you mentioned.

She may not need to eat yet. Definitely not unheard of in a rosy that age. She may resume come March.

Any changes lately? Stress is a possibility. Rosies "learn" their cages. As adults, when a radical change is introduced, they may stop feeding until they learn their new cage and feel comfortable. I've seen that. Babies adapt quickly. Older adults can take time.

A soak in 75-80 deg water is a good thing for captive rosies once in awhile. It hydrates them and gets things moving, if you know what I mean. I've raised neonate rosies up to big fat adults with no water in their cages - all water was offered in soaks. During drier season, every two weeks. And they almost always pass fecal matter then.

Hopefully her fasting is temporary. In the meantime, give her a basking spot of up to 85-90 degrees and see if she uses it, even sparingly.

Good luck.
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Mark