If he doesn't trust Avni then what kind of friendship is it?? Every time he suspected Avni She's proved innocent but he just doesn't want to trust her.In Riya pictures case he knew it wasnt Ananya and yet he concluded Riya as innocent and avni guilty.Riya was doing all that act yet he didn't doubt her a bit.
We still consider that he has genuine feelings for avni but he himself admitted that the friendship is fake n just for the case.
Avni is already too much betrayed n now Neil is doing the same.