I'd keep the "hot spot" surface to nothing over 90-91*- keep in mind that some digital thermometers can also be off by a couple degrees, & that "best advice" for BPs is to keep their heat to 88*-90* at the most. You don't need a heat injury (burn or neurological) on top of an RI, right? You do want more humidity- have you tried offering her a humid-hide? Soaks can be stressful (for the snake, I mean-).