Seyi Omooba will take the Curve Theatre in Leicester and Global Artists to court for breach of contract and religious discrimination.
Omooba, who had been due to play the lead role of Celie in the musical, made the assertion in a 2014 Facebook post that resurfaced in March.
The Christian Legal Centre confirmed to the BBC on Monday they will back her case, however the producers say they are so far unaware of any legal action.
In the offending post, the Londoner said she did "not believe you can be born gay", which led to the theatre company severing ties with her.
Now she believes she has been hounded out of her profession.
"On all my social media I always post stuff about god or scriptures," she explained in a YouTube video.
"They knew that I was Christian and they knew my stance on marriage, on my faith, on god... on many different things that are in the bible.
"I still can't believe it today, there was this massive opportunity - something that I never thought I would ever even achieve - and I remember the casting director telling me 'be very careful about where you go next because you have a very raw talent'."