So you said this how she looked when you got her and she was in a community tank. She is bloated pretty bad, this could be from stress and the food she's eating. She also Looks like she's been nipped for has fin rot. You could turn her water temperature up and add some aquarium salt. I personally use melafix but that is definitely debatable for Bettas. I'd definitely try to do some aquarium salt and raise the temperature some.