I still doubt she's a lesbian. Just because the sex with her was empty, doesn't mean that it's like that with all guys (and apparently that was her first time with a guy, so we wouldn't know anyway). Plus, how can we really tell? There were absolutely zero competing love interests for the girls (except for the track captain, if you count Hisao's paranoia), so there's really no reaction to gauge it on. This really just seems like WMG, making judgments based on little information, like the "Rin haz assburgerz!" thread.
edit: Apparently you responded to me before I could post my response, so I'll just add my counter argument here.
Bigbishounen wrote:
If so I doubt that the sex scene with Hisao would have been so incredibly uncomfortable and brief.
Maybe, and don't quote me on this, maybe she didn't care about Hisao specifically and just wanted to stick it to Shizune. Like I said, just because she had one bad sexual experience with a man, doesn't necessarily make her a lesbian.
She also mentions she'd never been with a guy before, so I'm not sure how you could say with certainty that she's bi if all her experiences up to this point had been lesbian ones.
No, she stated that she never had sex with a guy before. Big difference. Plus, there are bisexual women who prefer other women. Doesn't make them lesbian.
It seems to me that her sex with Hisao is more a desperate cry for help and attention than an honest declaration of bisexuality. And in the Shizune good ending this is made pretty clear. Misha admits that she didn't really want to do it with Hisao and she's gratified he turned her away. This starts her on the road to healing.
Like I said, probably just an effort to stick it to Shizune.
So yeah, still a lesbian (unspoilered because go finish the fucking game), and still not gonna be turned by the power of your wang.
Like I said, there's really no way we can tell if she doesn't like guys. We wouldn't have known that she liked girls if she didn't just flat out tell us.