Something interesting about this image that I worry might have gotten a little lost in translation is that the girl on the right isn't necessarily writing that to the girl on the left. She could be writing it to someone else (the teacher?) or just doodling a happy message on the board. The girl on the left is the only one actually looking at the other, so it's possible her love is one-sided.
Or I'm reading too much into it and it's just two girlfriends writing cute messages to each other in the classroom :)