Everybody has different feelings on what adults should and shouldn't do when it comes to personal choices in relationships. What's right for me isn't necessarily going to be right for you, or vice versa.
You're certainly free to say Claire overreacted in this case, but the fact is, she knows herself best and what will and won't work for her in a relationship. And we don't get to tell people how they're supposed to feel, especially during times of personal crisis.
If anything, her story is just a reminder that honesty — both with your partner and with yourself — is always the best policy for everyone involved in a relationship.