Talking through a movie is a huge sin if you ask me. Unless the circumstances are very specific (ex., you're at home with a close friend and neither of you really cares about what you're watching/have seen it before), then you shouldn't be talking through a movie. Certainly not a play. The actors onstage can hear you, by the way. Watching something at the cinema is an opportunity to have a deep experience with the art. You're disrupting that for yourself and others by talking through it. Everyone has different opinions on this, though, and some folks just can't keep it to themselves. They have something to say, and they want everyone else to know it.
The woman in this story was this kind of person who just couldn't help but talk through the movie. They had a running commentary in their heads, and they wanted to share it with the people around them. This isn't always the smartest thing to do, though, if you want to make new friends. You never know how someone is going to react to your behavior. You shouldn't change yourself for everyone you meet, but you shouldn't expect that everyone you meet is going to accept your behavior. Not everyone is going to like you, and that is okay.