I'm thinking the girl I like wants me to photoshop her picture with the guy she recently started dating since she knows me to do funny photoshops of her pictures. It disgusts me and I can't imagine looking at their pictures.
Why do you not want to photoshop her pictures if you're good at photo editing?
I feel depressed and dejected when I see the picture.
I understand your feelings that it's depressing to see pictures of the girl you like with another guy. It's ok if you don't want to process her pictures.
I'm going to edit the pictures and send them to her anyway because of my deep hatred of this guy.
I think it would be better if you just told her that you don't want to edit her photos. Doing so out of spite will only make you angry and annoyed, and maybe hurt your friendship with her.