If she is opening her mouth and chooses to remain under the light instead of moving away, she is not too hot. She is choosing to heat her body that hot on purpose.
Think about it- if she's right next to it, she can move slightly away to a temp that is a little less extreme but still warm- she could choose 80-85 if she wanted to but she isn't. She's choosing to be where she is.
Studies have shown lizards will give themselves a fever to help fight sickness.
Humans sometimes sit in saunas because they like it.
90 is not an extreme basking temp for a panther. It won't burn if it is only 90. IMO it is easier to keep a lizard healthy if they can heat up slightly above normal like this when they want. Every sun-basking lizard I've ever bred will do this from time to time- heat up and gape so they can remain cooking a little longer before moving away. They will do it indoors under lamps and outdoors under the sun.
"When they want" is the key.
It's fine as long as she can move away when she wants, and provided the heat is provided in a gradient so she can choose a range. It can't be an all or nothing sort of deal from using too low a wattage bulb too close to the basking site.