The person who drew this also draws a series of Touma/Yuriko comics. They're pretty nice to look at. I'll probably mean to upload them and never get around to it--anyway, my point is, I don't know much Japanese, but from what I can understand she really is a girl in these comics.
Not a trap, in other words. Calm your jowls, brother, it's all gravy.
Is genderswarp. In the novels things hapen a little diferent in minor details or were censured in the anime one of these is that Touma is VERY nervous for the beginin of the classes cause he can´t remember his classmates and has a nigthmare of Female Accelerator bein a classmate wich totaly freak him out but thanks to the increidible populariti of this event femAccelerator got a name please note that the original DO NOT HAVE A FREAKIN!!! ONE so yehaaa you got the idea