She says this even though Puerto Ricans are US citizens? Even though they're not from the continental US, but neither or Hawaiians or Alaskans 
She doesn't get it. She thinks that if they speak Spanish, they must be immigrants. That's where the reminder about Puerto Ricans come in. But the whole thing is, I imagine that the county offices are mainly full of English speaking Americans of all races, but one or two Spanish speakers stick out in her mind.
She's that way though. Once we pulled into a petrol station at about 2 am. A guy pulled in with his stereo blaring rap. Now, I don't care what the person was blaring, at 2 am in the middle of an urban centre, you ignore it. Well, she started screaming at him whilst pumping the petrol. The guy totally ignored her, but she was going on and on about that "crap". I was at once mortified and scared. She was totally profane and aggressive. Thing is, I know she wouldn't have said a thing if he was blaring Kenny McManurekickers or whatever. Or if she did, she would have told him how much she loved that song.

We've never let her or her partner be comfortable with their prejudices and have challenged her on this and a tonne of other things. However, I don't think we will change her that much. At least she knows that not everyone agrees with her.