Come to think of it, the term 'betrayal' is quite ambiguous. For the case of Hardy and Shelly, they will probably only join if Meteor threatens the person they are close to (in this case, Aya and Heather). Then, they probably wouldn't have any choice but to join them ie they are doing it very reluctantly. I guess the 'shock factor' is still present if they do join - but does that really count as 'betrayal' if they had no choice?
Thats why I'm leaning more towards Aya and Serra (I like your theory on her, Hilda). The shock value would be much greater than Hardy - especially if they are like "Ohoho I've been part of Team Meteor all along!" then yes, it would be quite shocking. I'm moving away from Radomus though. Lots of people seem to trust him - and but there are still lots that suspect him. I have a feeling the 'betrayer' is going to be someone that only very little people suspect.
...but then again, my predictions always turn out wrong lol.
...btw am I making sense? It's almost time for me to sleep so I'm probably not saying things clearly enough