Obviously all of us have the right to feel however we feel, but that doesn't mean those feelings are reality. They are valid and they exist, but they do not always reflect REALITY, which is that no one is a "failure" for having a C-section.
That's where she and Darren fail in communicating with their audience. They state their opinions and feelings as fact when they are NOT. The response to this comment would have been, "Of course, no one is a failure for having a C-section. The measure of success of a mother is in the raising of her children, not how they were brought into the world or her life. My emotional brain is just telling me that I'm a failure, but my logical brain knows this is not true and I'm working on making that voice the prevailing one."
Speaking as someone who is also working on fixing my anxiety, this inability of hers to identify illogical and harmful thoughts is a major reason why her anxiety is not getting any better.