That's about my setup. 20 long with 2 hides, water dish in the middle, and a random rock she likes. I'm getting my table lamp dimmer tomorrow to control the temp on the hot side. It's unplugged right now but the temp is only at 78 degrees in my house, not too worried.
I would assume that just like BPs they need the heat to digest so that makes since that she would go in the hot hide. I'm figure she'll do what she wants when she wants. LOL