Considering I'm actually trans in the realz, I would have to say I think you're taking that out of context.
The other user said-
"No, the mind does not change, if you are a man and suddenly you are in a woman's body, you are still a man, if you follow this body logic, lesbians and gays should not exist."
My point was...I think its possible the mind could change. I mean, the mind and body have a huge influence on our behaviors, way of thinking, and overall lives. The other user saying that "the mind does not change" (at all) is very narrow minded IMO.
And susie either doesn't seem to care or actually seems to like it. I would lean towards the later since Susie tends to be a bit too into it in various ways. (I think Susie was probably a soft or closeted trans person themselves tbh, judging by their statements in the webnovel. I.e, they felt that their character was more them than their own real self/life. And that they could be their true self when playing as Susie).