Who's that girl? (Patreon)

So, as I mentioned earlier, the next project is going to be a collaboration with me and another artist. It's gonna star Rebecca and one of his characters. Above is a picture of said character, can you tell who it is and who does she belong to? I think that lot of you know her. As always, winner gets a (virtual) cookie!

http://i.imgur.com/HetF0qq.jpg