I'm going to be the contrarian - surprise surprise - and say she holds her own. You know the moderators will coddle her along, so she has that advantage. She also has the advantage that her supporters have extremely low expectations, so it's not like she has to be intelligent or knowledgeable. All she really has to do is keep her cool and not go off on any kindergarten teacher tangents. She'll smile and laugh a lot, and have a couple of zingers in the queue.
I kind of think she will.
I saw - someone - I think it was Doug Schoen - saying she has almost certainly memorized certain talking points, which she will insert without any regard for the question asked. I said almost exactly the same thing - she wants her "moment". She will give lawyerly long-winded NON-answers to questions she fumbles on, but her supporters will be so in awe of, they won't realize it doesn't say anything. And she will insert campaign promises and criticisms of Trump where it has nothing to do with the topic.
And the moderators will not only be ok with it, but they won't PUSH the matter, when it doesn't answer the question.
They WILL push back, on Trump. For his part, he POSSESSES the ability to show "gravitas", that word so overused regarding Dich Cheney - the seriousness that says "price controls don't work, government spending and printing money caused inflation, three and a half years, why should anyone give you more time?". Nope, he's going to brag, and be the showman. Hoping he won't, but he's so cocky, he's gonna wing it.