I think a "
Highlander meets
The One"-stye IB story would be freakin' awesome. Except, you know, the girls would have to do something to each other a bit more fun than cutting off one another's heads.
The heroine would be a plain girl who found her self becoming inexplicably more beautiful over the course of months- until an evil duplicate from another dimension appears to "cut her off from the source of beauty" or some such. The heroine could lose the initial battle and become downright asexual, causing her duplicate to become even more beautiful- but afterward would pursue her copy into the next dimension, encountering further versions of herself of widely varying morality, finding out what this 'source' thing is, and tapping back into it to gain the power to face her nemesis twin in the final confrontation.