I would write down her "quirks" or "traits". Write down behviours over a few days, what happens when you go to the shops? What happens when you try something new? How is she when you meet new people, is it just shyness or is it something different, how is she afterwards?

We used to have shops hangovers, where she'd actually behave, but then would have issues for hours afterwards...

Food traits, what happens with food, what is her diet?

Sleeping patterns and traits....

I would look up Sensory PRocessing Disorder and find a check list, go through it and bring it with you. Very Very important.

Good luck!!

BTW... have a look at our Sensory Processing Disorder/Autism/Aspergers thread and have a read at things that have happened over time for those going through the diagnosis process.