'De-gaying' is a term used in the media for the removal of gay/lesbian elements. For example, if a production company adapts a book to make a film and changes a gay or lesbian character into a straight one, they have 'de-gayed' the story. The reasons for this are purely practical - it makes the film more acceptable to a larger proportion of the movie-going public of the USA.

It is not a real word per se, it is probably just a way of saying that someone was made to not be "gay" (meaning homosexual). It would be hard to say for sure without seeing it in context. You can add "de-" to just about anything to signify removing. In the winter we "de-ice" our car windshields, for instance.

This is an invented word which means to change someone who is homosexual into a heterosexual. 'de-' in English means to take away or negate, much like in Spanish. The writer here took some creative liberties and and applied it to the word 'gay', or homosexual.