Good for you for trying!

In your shoes, I think I would write exactly how long it takes her. Being sort of snippy about such things, I might add a note saying you had tested her and she fully understands it, reads it fluently, and can recite it forwards and backwards. Okay, maybe not the last bit...

I'm still so confused by what the school thinks they are doing by holding readers back and keeping everyone at such an artificially low level. How can it help their testing, even? I think I would have to meet with the principal. This is so completely different than how DS' school has approached reading.