Most (not all, I know some very great and knowledgeable places) pet store employees should be listened to with a grain of salt. I had one PASSIONATELY try to talk me out of using a UTH because apparently they always burn the snake,` even with thermostats and if I do I should use 6" of substrate or something. Whatever.

I say go tub; it has way more benefits if you don't care about display. HOWEVER, the one issue there is with tubs is that you can't use lamps for supplemental heat, so she'd need to be in a warmer room or have her own space heater or something. That being said, there are ways to maintain tank humidity, but tubs are easier to maintain and clean in my opinion, plus way more room.