You need to keep a pair of foam ear plugs for such situations. I stopped going to church music services because it would take all day to recover, even with ear plugs.

Your girlfriend needs to accept the fact that that volume of noise is not healthy for you or for anybody in the auditorium. The tinnitus may reduce. Nobody can say.

btw, At my church, they have an alternative room with a video screen and sound volume at a reasonable level. Many seniors and others sit there because the sound volume is so intolerable in the main auditorium.