It's not the crossdressing that makes her suspect, but the fact that her charge is a very openly bisexual hedonist who sleeps with most of her servants, male or female - all of which are quite happy with the arrangement. She tells Osaka that the correct term is 'lesbian,' then says her attraction to Sakaki is 'a teenage thing' adding she wouldn't mind if Sakaki were a guy. The closest the series comes to addressing the issue was when Osaka asked Kaorin if she was gay, in the '10th Anniversary Omnibus'. Moe compares them to a married couple, while others tend to see their relationship as platonic.
While everyone in the cast knows Mira and Ao are very close, they have different views on the nature of their relationship. An In-Universe case appears in Asteroid in Love.
