Check the temperatures, both basking and air temps. If these have dropped, could be brumation. How about her overall condition? Does she look like she does when she's sleeping at night normally or is she really dark? Has she lost weight? Where is she hiding? What were her last poops like?
Bearded dragons sometimes go into brumation even if the cage temps are the same as always. What is really important to watch for is to make sure the dragon isnt' slowing down for other reasons, like parasites, impaction or illness. If you are not sure, then take her to a vet to examine.
If burmation is what she is doing you cna reduce her light from 14 hours a day to about 10 hours a day and don't feed at all. If she comes out then you can offer a small meal. I wouldn't offer alot as sometimes dragons will go back into brumation after being up for a few hours. I would just offer fresh greens instead of insects, or a few silkworms, more to ensure moisture than food.
More information about brumation can be learned by doing a search in the forums.
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PHLdyPayne