Okay, so I was strengthening my adjectives and when I finished it said I strengthened adjectives ,but it had a picture of the "flirting" bonus skill. The flirting wasn't full bars ,but when I exited and saw on my tree that Adjectives was strengthened. It did the same thing with colors.
After I complete a lesson that doesn't result in full strength bars in any Skill set I receive the message "You strengthened [Skill name]" + the image of the Xmas bonus Skill set. I've made an image here: http://imgur.com/VQOei0H The only time I see the correct image is when I complete the strength bars of a Skill set. Image here: http://imgur.com/4fEpcIU To the record, Xmas Skill was the first bonus Skill I added. Was "Flirting" yours?