I think she is criticising the idea that there is one "truth" of trans, that either dysphoria in children persists and is a sign of true transness or that it doesn't and therefore the truth is that "trans" does not exist. And therefore also disagreeing with the idea that science or data can be used to arbitrate between these.
She just doesnt address what "trans" is. Or that it's often used as an umbrella term which means that there is no such thing as "authentically" trans since it can mean more or less anything, much like queer. But then again she also describes mumsnet as something like "a mommy blogger site." so defining terms is either not her strong point or perhaps not relevant to her own thoughts or those of her intended audience.
Bearing in mind this article is from fourish years ago when she was 20ish, writing for what looks like a student publication with writers who self describe as predominantly queer women...
I think it's not as frothing or as rigidly ideological as might be expected. I wonder what she thinks of it now?
One thing I would take issue with is her lack of empathy for parents and the use of parentheses for "concerned". And as someone else pointed out, the information that she went to the Tavistock as a teenager doesn't really say much about her parents and their opinion of all this. Plenty of parents took this route. I wonder what she'll think of this if she ever gains the life experience that is being a mother?