It ain't easy coming out on the spot. It's her fault for asking about it but she was not prepared to respond properly. Fumbling her words and not knowing how to pull herself together so she doesn't seem like a phobe. Glad wan picked up on xin being nervous, for some reason ;3, as a closetted thing rather than a bigotted thing.
It's almost like wan acted annoyed on purpose to coax xin into proving she's just nervous about the topic rather than a bigot.
Honestly? I have suspicion it is acted, her expressions when her wrist was grabbed and doing a 180 from "are you homophobic?" to "are you gay?" gives impression this entire conversation was planned to probe on Chao Xin sexuality
As a matter of fact I feel it's a intended contrast between them, we get a few times of Chao Xin talking on how because Xiang Wan is young she looks out of place, inexperienced, stumbling around life and so on in but at the same time we're getting the clear picture that Chao Xin is stumbling around life just as much but in other aspects even though shes older and the supposed Adult™ of the two
I think this will be classic top young lesbian helping the older closeted lesbian realize her own sexuality