The general consensus seems to be that the max temperature anywhere in the enclosure should be 90F. However I have also heard of some variation on this including from my vet who told me younger snakes sometimes like slightly warmer temperatures and some people provide a temp gradient between 76-93F although I have also heard people say 93-94F is way too warm. As long as the temps are correct and are being properly measured throughout the enclosure (which it sounds like they are) and she can't actually get burned like mentioned above I would agree that it's fineShe's choosing to be up there so that must be where she's comfortable.