Anguirus is not female. Godzilla: Singular Point never refers to it as a she. The subtitles that are spreading around are either machine translated or amateurly done, and Moyai Subs' work is much better.
The line here is "It's coming this way" (こっち来るぞ) - nothing gendered about it. For whatever reason these fansubs decide to consistently use "she" for him. Perhaps it is a problem with Google Translate, which seems to basically pick pronouns at random when translating Japanese-to-English.
I hope this clears up some confusion.
