I the plot like this: Boy meets an alien flower of sorts, I think, and is granted one wish, but his wish is to become a girl. The plot follows him becoming a girl. He was also in love with his best friend?? IIRC. q2tx

The mangaka, as I was at least at the time considered a woman (but it might have changed since X-gender came out since then) and was relatively well known for her other works, but this was a more minor, lesser known one.

The manga explores sexuality along with gender ID and I think it's a shorter series.

It was never made into an anime.

Uh sounds kinda like Kanojo ni Naru Hi (in love with male best friend, gender change, female mangaka) but I don't the alien flower bit (or mangaka gender spectrum) so might be something else

Sounds really close to Blue Drop or one of it's off-shoots in particular. Though the second part of your post makes me think it might not be his work you're after.

I found it. It was https://mangaupdates.conexionsite.com/series/spd1eat/blue-wars by NAKAMURA Yoshiki

Thanks for your help, though.