Bubbles from the mouth could be a sign of a respiratory disease, which may require a vet visit. That could also be a reason for the loss of appetite. Is her activity level still good?
As to food, kale is on the list of moderate, but not regular, plant foods.
http://www.redearslider.com/plants.htmlHowever, if she's not eating pellets, you may have little luck with kale. My turtle is a pig, but hates kale.
You can try soaking some pellets in the water from a can of tuna. That should make them much more tempting. As Steve mentioned, live prey is also a possibility.
Even more than a week without food for a healthy adult RES shouldn't be a problem.
We're there any other changes besides the heater going out? Did you recently open a new container of pellets? What is the substrate? There are reports of RES eating aquarium gravel, which can cause problems.