One line that I noticed missing from your original post was:

"We let everyone know that we were new to the run, and would appreciate any guidance."

Did this happen? Or did you start the run off with nary a word, and no idea what was going on?

When you're new to an instance, it's a good idea to let people know that you are new. They will be more forgiving of your mistakes, and in general will give you advice and guidance over the course of the run, especially if they see you struggling. There's a lot of folks who will join a raid and simply not participate, letting the rest of the group carry them through and picking up free loot along the way - these people are regularly kicked if they are caught doing such a thing, and your S.O. may have been mistaken for such an individual.

There are horror stories on the forums about people who are kicked from an instance because they are new and the "elites" don't want to have to babysit them. I've never personally seen this happen, and I suspect it's quite rare. Most players are helpful, and require a trigger before the PG13 language starts to fly.

Remember, it's not the responsibility of the other players to explain the mechanics of a run every time! In the vast majority of runs, everyone already knows what they're doing (and, likely, has completed the run many, many times over), so the assumption is that if you don't say otherwise, you know what to expect!