Hi pendulum- I was right where you are now with my DSD a year ago.
We have started an ASD assessment with CAMHS at the beginning of 2012. We're right in the middle of it now.
I would echo what was said above about Listing your concerns. Be honest and list the things that you find unusual before you approach a Developmental Paed or your CAMHS teams, if they are have an ASD Clinic. This will give you a base to work from and something to start the discussion.
From what I read in your description; there is rigidity in thoughts & play (need for control, going on about a subject), sensory issues (shoes) and an awkwardness with social interaction. That would be enough for me to warrant an assessment.
Since your DD in now 8 and secondary school is looming, I personally, would seek an assessment. We always brushed off DSDs quirks until she started secondary school, she then pretty much fell apart when all the rules had changed and had a very tough time adapting to the new routines etc. Girls take longer and are harder to diagnose so if you are worried, by all means do investigate it.
Don't be afraid to read on the subject, I've already adopted ASD strategies as ineedalife mentioned and we have had success with them. Tony Attwood is excellent read as well as Aspergirls by Rudy Simone.
I will quote Tony Attwood as Babyheave did for me when I started questioning about DSD, it was a significant moment for me and I realised our daughter, was different and we owed it to her to explore her quirks and differences, to ensure she would be better understood and get the support she deserves.
"In early childhood, probably long before a diagnostic assessment, a girl who has the characteristics of Asperger's syndrome will begin to know she is different to other girls. She may not identify with or want to play cooperatively with her female peers. Her thoughts can be that the play of other girls is stupid, boring and inexplicable. She may prefer to play alone so that she can play her way. Her interests can be different to other girls, not necessarily in terms of focus, but intensity and quality. For example, she may collect over 50 Barbie dolls and choose not to enact with her friends from the neighbourhood 'Barbie getting married' but arrange the dolls in particular configurations. There can be a determination to organise toys rather than share toys and also not play with toys in conventional ways. She may prefer non-gender specific toys such as Lego and not seek acquisitions related to the latest craze for girls her age to be 'cool' and popular. There can be an aversion to the concept of femininity in wearing the latest fashions or fancy or frilly clothing. The preference can be for practical, comfortable clothing with lots of pockets. While boys with Asperger's syndrome can fixate on facts, and some girls with Asperger's syndrome can also have an encyclopaedic knowledge of specific topics, there can be an intense interest in reading and escaping into fiction, enjoying a fantasy world, creating a new persona, talking to imaginary friends and writing fiction at an early age. Another escape is into the exciting world of nature, having an intuitive understanding of animals, not people. Animals become loyal friends, eager to see and be with you, with her feeing safe from being teased or rejected and appreciated by her animal friends.
There may be single but intense friendships with another girl, who may provide guidance for her in social situations, perhaps in a benevolent way and in return, the girl with Asperger's syndrome is not interested in the 'bitchy' behaviour of her peers and is a loyal and helpful friend. Unfortunately, sometimes the girl who has Asperger's syndrome is vulnerable to friendship predators who take advantage of her naivety, social immaturity and longing to have a friend. Inevitably there will be times when she has to engage with other children and she may prefer to play with boys, whose play is more constructive than emotional and adventurous rather than conversational. Many girls and women who have Asperger's syndrome have described to clinicians and in autobiographies how they sometimes think they have a male rather than a female brain, having a greater understanding and appreciation of the interests, thinking and humour of boys. The girl who has Asperger's syndrome can be described as a 'Tom Boy' eager to join in the activities and conversations of boys rather than girls.
Happy to discuss further if you want to PM me and ask questions.
Hope this helps.
Also, have a read on the Special Needs section, lots of ASD parents on there will be more than happy to share their wisdom & experience.