Why does my 3-month-old get hot and sweaty when she doesn't have a fever?
Babies usually sweat when they are overheated, so the first thing to do is make sure you aren't overdressing her. They sweat around the head and neck, as sweat glands in other parts of the body are not as well developed. As to the eating, 3 months is a transition time for babies. She may be doing things a bit differently, such as spreading out her feedings. Biting is common at this age, as babies learn to explore their mouths. When she bites, stop her and just say "no." She'll soon learn that biting isn't acceptable behavior.
Bring her into her health care provider for a weight check to be sure her growth is on track. That's the best way to know if she's eating enough. I doubt that she's teething; that will start a few months from now. Overall, it sounds as if you are in one of those shift periods with your daughter when she suddenly seems like a completely new person and you have to make some changes with her. There will be lots of those times ahead.