Is it supposed to be a different girl in the reflection?

no?

At least both views aren't in focus so it's not bad enough to be noticed at a glance.

Incidentally, her name is Fujino Karin.

Ralated to this doujin:

• http://tohoorin.blogspot.tw/2015/01/lovely-lolita-only.html
• http://goods.ruten.com.tw/item/show?21506429144356

CharsDeleted初号機 said:

Her face appears to be obscured from the mirror by her hair on the right side, ＩＲＬ, but in the refection, one can see her face and both her eyes looking back at her. The tip of her shoulder ＩＲＬ seems to be parallel to the tip of her nose (suppose one drew an imaginary line extending from each), but in the mirror, her nose and shoulder appear to be 'pointing' out to different directions. That twintail that is hanging over the front of her body should not be visible in the mirror, considering her facing away from the mirror ＩＲＬ.

Hence, the most incriminating thing is her knees. ＩＲＬ, they are visibly separated, but i(sic) the mirror, she appears to have her thighs down to her knees pressed against each other.

Quote extracted from this image on the Gelbooru sister site.

The knees aren't that bad. It's a matter of bad perspective. The reflection doesn't show them actively touching, and the shading could be coming from the light source that appears to be at the base of the mirror. More of a bad_perspective thing. It's definitely an impossible reflection angle, though.

Ideally, we would split up different kinds of reflection mistakes. Impossible angles, different traits, and copy/pasted objects. But it seems like there aren't enough items to justify it.