Newsflash: Freddie Mercury was a bisexual man who was in a long term relationship with Mary Austin. Many of his hits, including love of my life, are about her. The movie will most likely portray that relationship as well as later in the film, his relationship with Hutton until his death.
You thinking that freddie having a girlfriend in the movie is homophobic is actually biphobic and bi erasure. Bisexuals can date people of the opposite sex and still be bisexuals.