If we're talking about common plot scene with Seth where he was slapped, it's not like Maria had any choice. Veronica ordered her to do it...Although personally, this scene angers me. With regard to Seth, this procedure could have been made less humiliating, but Tess decided to show it this way. I usually defend V, but this particular scene is not her style at all, and I definitely don't like it.
As for Nurse Reyes, I have no idea what she does on the sub route (probably nothing good), but on the Dom side she seemed pretty sane to me and not as sadistic as Jules' minions. So in all my Dom playthroughs, I saved her from death...Let's see how she behaves next and how grateful she will be.