I wouldn't say this manga is wrong in the way it describes gay people. I'm not sure how old this is, but it's clearly an old-school yuri, you have to consider that homosexuality wasn't always seen the way we see it nowadays. It's still pretty progressive - it depicts openly gay characters (both men and woman), butch lesbians, and the protagonist is either a lesbian in denial or bisexual. It just has that bittersweet feel of old yuri.
Also, I felt a little bad for Tracy. Her love remains one-sided at the end... and I would have liked to see if Chelle was really as annoying as she is described. Poor girl has cancer, she probably had very good reasons to be clingy lmao