I dont think there's anything fishy about it. Aamir always respects girls a lot and very humble. And the song had Additi's name, so dey dedicated it to her. As for him telling her to smile last mein, it was coz of the same song itself. If you see, these 2 episodes are shot on the same day continuosly. Also Siddesh was attacking Mukti-Additi's dance that dey scored equal in spite of Boys dancing more than them(according to him). So again Aamir must hav told additi to smile coz of the same song "kabhi kabhi additi" coz she did seem surprised. I dont feel anything fishy over there...just my POV!!
i second what nansy said. there is nothing much to speculate it is pretty much clear why aamir asked addite to smile.siddesh was asking the girls to dance in sync in the zara hatke round even after addite and mukti gave a splendid performance that got them 57 marks wich is the saem as what the boys got in the zh round. they showed addite's face when siddesh was telling this and she os looking really tensed. and hence amir asked her to smile.aamir said that girls performed well and siddesh spoke in the spur of d moment because he had to prove himself once more to be in the competition.
and if u notice none of the girls were as tensed as addite when they were all standing onstage.reshmi was fuming with anger but she was not tensed .
(dere was a precap before addite's and mukti's performance and in that they showed a tensed looking addite and i was really shocked and thought she messed up her dance but then she performed well .the channel was just trying to build up more tension in our minds and they had shown the clip wherein additewas sad whensiddesh was talking abt girls not dancing in sync )
i hope everyting is clear now!!