I think florent & maeva used to be special to each other .. i mean just write "Florent Mothe / Maeva Meline (Mozart l'Opéra Rock) : "You" (Compo de Florent Mothe)" on youtube and watch the video :p
First of all, all those video clips are made by fans which means that there are no facts in them what so ever. Those videos are fans’ subjective point of view on the topic. Their wishfull thinking. Nothing more nothing less. IThey don’t prove anything. So it doesn’t matter how many videos like the one you’ve mentioned there are unless it was filmed by Florent or Maeva.
And secondly, I have no idea if they had a relationship or not. But even if they did, so what? What’s the big deal? They are young, beautiful (both outside and [I’m sure] inside) people. If to be happy at the time they needed each other and got what they needed I’m happy for them. If they were together and for some reasons decided to split up and managed to save their friendship and to be able to work together… Good for them. it’s very hard and therefore very rare. And if they find someone they want to share their lives with (each other again or someone else) I will be happy for them. Whatever/whoever makes them happy…