Forget aarti.
The biggest proof is that when Sidharth talks about stuff from outside he talks straight up in front of Rashami loud enough for her to hear. She doesn't say crap back then. Rashami sits around and discusses crap about Sidharth most of the time when he's not around to defend himself.
Why didn't she defend herself today?
ETA: Rashami also mentioned how she's scared today. If she spoke the truth, why is she scared?
I think she is scared he leaks out some intimate info she did not expect Sid to go to this level!Even what she mentioned was meant for Arti she was not poking or targetting Sid when she said about him saying sorry!