Areloch said:
The conversation makes it sounds like she's pretty confident in it (again, coupled with the fact that she just decided to read young iceman's mind about this topic, so I honestly wouldn't be surprised if this version of her does it whenever).
To be fair, she probably spends more time with young Iceman and his constant overcompensation probably prodded her along.
Bobby: "But my older self ISN'T. We've met him"
Jean: "I know"
Bobby: "So..."
Jean: "Buy you-"
Bobby: "Stop"
Jean: "Are"
That's Jean - for whatever her knowledge on the adult version is worth - stating that she knows he isn't gay, but young Bobby is.
Eh, I can see that "I know" being less of an "I know he's straight" and more of an "I know it's hard to believe" or "I know this is hard," though it could, like you said, just be inconsistent writing. Maybe it'll get cleaned up into something less weird if they still have the chance, but, if not, it's not like this would be the first instance of dumb writing happening in a comic.