That would be fine, jno, but having already accepted the job, refusing then to play it as requested is refusing to do the job properly. If a homophobe refuses to play any gay characters before accepting the role, then that's their free choice; although, given the publicity surrounding this case, I doubt she'll find employment in acting any time soon.
It isn't a "script change" either -- part of the theatre's case is that (a) this was already a clear elment of the story, as affirmed by its author,(b) she hadn't read the script they'd sent properly, (c) other productions have made the same interpretation, including one Omooba was previously involved in.
Moreover, if you stick by homophobic comments then you are essentially making them afresh. That's toxic both for the working environment and, in this day and age, for the company itself to be seen to tolerate such bigotry.