It appears there might be a reason for that to do with the studio, and that the filmmakers would have really liked to have been a little more open about. The Daily Beast asked director Paul Feig straight out whether Jillian is gay, to which he answered, “What do you think?”
When the intereviewer says that they think the answer is ‘yes’, Feig reportedly silently nodded and said, “I hate to be coy about it. But when you’re dealing with the studios and that kind of thing…
“You know, Kate is who she is and I love the relationship between Kate and Melissa’s characters,” he says. “I think it’s a very interesting, close relationship. If you know Kate at all she’s this kind of pansexual beast where it’s just like everybody who’s around her falls in love with her and she’s so loving to everybody she’s around. I wanted to let that come out in this character.”
That would suggest Jillian is supposed to be LGBT, but they’re not allowed to say it.
While Star Trek Beyond is making Sulu gay, generally Hollywood is still terribly afraid of having openly LGBT major characters in its big budget movies. The fear is that inclusion will affect the box office – or indeed get the movie banned – in countries where homosexuality is still frowned up or illegal, and may well deter anti-gay elements in the US. As hundreds of millions are being spent on these films, they simply won’t take the risk.