High fluid reasoning, even if prevalent amongst people with aspergers, isn't part of the diagnostic criteria.
What is it that makes the speech therapist think that she is on the spectrum? Are you having difficulties at home aside from speech?
Here are the diagnostic criteria for autism and aspergers, at least in the DSM-IV (I don't know when the DSM-V is scheduled to come out but I recall there may be controversial changes to this section?):
http://www.cdc.gov/ncbddd/autism/hcp-dsm.html I don't know a whole lot about Asperger's, so I'm sure someone else will chime in, but according to the diagnostic criteria, a speech delay is contrary to the diagnosis. My understanding of autism, aspergers and the spectrum is that they are predicated on significant social impairment. A very, very bright child with a speech delay and sensory processing issues is not necessarily autistic or having aspergers. I like the Eide's book The Mislabeled Child, which explains the differences between many such issues, and as far as autism goes, they focus on a severe lack of emotional empathy.
FWIW, I think the DSM is poorly drafted in that it's confusing, and I also think that our understanding of these issues still has a long, long way to go.
Unless your daughter is experiencing significant problems unrelated to speech itself, I would not be one to go looking for a diagnosis.
