What size tank is she in? Is there a filter, heater, water conditioner being used? What decor is in her tank with her?
Her fins look a little clamped so I'm going to guess she is stressed out. I can help more if you are able to answer the questions posted above.
Just a little I can give you now: Bettas like warm water (72°-80°). They tend to be more active in warmer water.
Bettas need some type of filtration just like any other fish. You can get away with not having a filter if you are willing to do daily water changes.
Bettas are very intelligent fish and like decor for stimulation and hiding. If there are areas for her to lie in and hide in she'll do much better.
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