Absolutely correct.
Some time back, I used to serve at Mass during the summer where we go on vacation. One time the priest came in, and explained to me before Mass that he had a sore throat and could barely talk. He could say the Mass, because it would be valid even if people couldn’t hear most of it. But he asked me to read the Gospel as well as the Epistles.
In the circumstances, I agreed. But I must say that I felt uncomfortable about doing it, and briefly explained to the congregation, who hadn’t been told, why I was doing it at our pastor’s request.
Absent such an emergency, there is no excuse for anyone but the priest or a deacon to read the gospel. Especially not a nun who evidently does so by her own “authority.”
What is the logic behind that? Teaching I can see as that is what Paul commanded. But reading Scripture in a service isn't allowed by anyone but the above?