Ugh, that's horrible. I hate how Walmart and petsmart have their Bettas on shelves that are under others. The fish don't get light and, since its harder to check on them that way, they don't receive decent care.
I hope the shock of going into clean water doesn't kill her. Are you gradually going to shift he over?
Hannibal: Male Baby Betta of Unknown Fin Type
Tonraq: Male Half-moon Dragon