Hi, I cannot reccomend a book but just wanted to say she does not sound too dissimilar to me when I was young. My shyness was so bad that if we visited friends of my parents who I didnt know really really well I would sit in the car outside rather than go in.
I also wet myself on at least 3 occasions that I can remember because I was too scared to ask to go to the toilet - once at majorettes, once in a school test and once in the queue for pick and mix. How embarassing is that???
School trips were an ordeal,and I can clearly remember on one choking on some food because I hated it and didnt like to say.
I am pleased to say that I am now very confident and when I tell people I am actually shy they laugh at me.
My turning point was a junior school teacher I had. He really encouraged me and gave me loads of confidence, praised my work, picked me out to answer questions he knew I could answer, but never made me feel concious of it ifkwim. I still sometimes feel out of depth on formal social situations, but I am 1000% better than I ever thought I would be.
In hindsight I wish my parents had pushed m a bit more, and I had been more inclined to take chances. I went to playschool once, told my mum I didnt like it and never went again. I wish she had made more of an effort. However, that is easy for me to say now and it might have had the opposite effect at the time.
Think I jus wanted to say, your dd may well be fine, just really shy.
Hopefully someone else will be along soon with some more practical advice.