Gareth Bryne is one of Egwene's underlings, Gawyn was not. Gareth Bryne disobeyed Egwene's orders, Gawyn was not under Egwene's authority for her to submit orders to him in the first place. Actually, I get that she is displeased with Gawyn for not trusting her, but she didn't make much of an effort to communicate to him or let him understand either, and she was in no position to stop him from doing what he thought was best either. Bryne, on the other hand was in clear violation of his duty to her. It seems to me her reaction to the two should have been inverted.