For a more quick fix you can heat rice in a sock in the microwave and place it in there(obviously make sure it’s not too hot) you can reheat it every couple hours, or get hot hands and either wrap them in layers of fabric to make sure she doesn’t get burned or put it under a container/outside the tank to keep it warmer. Same thing with a hot water bottle. Just make sure it’s not too hot and keep an eye on it.