Congratulations! I just need five more diamonds to finish the event. Does it unlock the ability to buy additional rose screens when you finish, like it unlocked additional lamps with phase two? I ask because I've seen people with more than four screens in screenshots.
Look at the second post of the current Screenshots page (page 20 for me). That girl has tons of screens! Maybe it’s a cutscene like you say, because why is she able to hold the guitar?
Edit: yeah, you’re right. Lol. Lottie being in the picture should have been my clue.