She must have been a later instar when you got her if you've had her since December and she's already had her final molt.
Did you mean to say the humidity drops to 11%? A good humidity range for this species is 40-60%. This particular species is very susceptible to illness due to excess humidity. With live plantings that level can be tricky to maintain. I can't imagine a bioactive enclosure dropping that low... unless I'm missing something.
No offense to any pet shop employees, but unless they specialize in invertebrates I'd also do a little research on my own to make sure the info is accurate. Can't hurt to double check.
Hopefully she will be OK... I've seen worse cases that didn't result in death. Keep us posted. Hopefully someone with more suggestions might chime in.