If you are adamant that she no longer qualifies then a quick letter when her renewal comes up will probably do it.
But please think very carefully. When I was very small I rarely spoke to anyone other than my mum and then I rarely initiated. Mum would go with me to playgroup and until the age of 5 I would ignore all the toys and other children and just run round and round the hall and then try and escape out of one of the doors. My mum was known as "poor Mrs X" as I was such hard work. I would throw violent tantrums. I was, thinking about it, harder work than my Ds1, who is further on the spectrum than I am. I started school and would chew on other children's pen tops (they held a meeting and banned me from borrowing them again ).
And then I got to six and from that age until 10 I improved a fair bit. I could play tag in the playground and be invited to tea. I could attend Brownies and join in with the PowWows and the activities. I could sit in lessons.
And yet, despite these improvements, there were still differences and difficulties which were picked up by others. My handflapping for example, or the fact that if an adult asked me a question I would answer them by speaking to my mum. Or my constant daydreaming, my inability to pick up on even basic things, the fact that I still rarely initiated things or asked for help or for things I wanted. My passive nature hid a lot of things, but not enough to prevent the head master of the school picking up on the fact I was different.
The thing is, is that during this time, between the ages of 6 to 10 I think that my immaturities did not matter to others, or were as apparent to others. Females who are Aspergers often present as immature, rather than the classic male stereotype of being more direct and inappropriate with their talking. Now, if you have a six year old who likes playing tag and you have a ten year old playing tag, neither one will be held to be unusual. However, if when that girl reaches the age of 11 or so and the other girls start sitting around gossiping rather than playing games, then the gap between a girl who has AS and girls who are not on the spectrum becomes clearer. Tony Attwood wrote a very enlightened piece about girls with AS, yet he failed completely to understand that, far from, as he put it, other girls being "maternal" and "caring" to AS girls, they can, in fact, be vicious little bitches. I finally, in the VI form, found myself again able to interact during breaktimes when I started playing football with a few lads. Had I had been able to do this at secondary school, rather than being trapped between realising I was supposedly too mature to play games and yet was too unable to interact socially with others, I would have had a far easier time of things during those breaktimes. The main thing I remember from my school days was that I changed very little i nterms of social an emotional aspects, from the age of about 6 to about 14, getting a vague interest in boys being about it. What caused difficulties for me was that other children did change and so the gap between me and them widened. So basically, what I'm trying to say, is go through your dd's diagnosis with a fine toothcomb.