It totally is but I have no clue who it is. I've only seen two eps of Kobato and wouldn't even remember the series name if it weren't for Drill Sgt. Snoopy. But the only pic tagged Kobato she appears in seems to be the one you linked to and there's no sign of her on the official website.
It's a shame. I think a cutie like this should appear more.
Finally found her. She's from the light novel series "I don't have many friends" （僕は友達が少ない） by Hirasaka Yomi. The main character's little sister. You can find some more of her on pixiv.
