Painstakingly Shy

Ok, friends, I need some advice.  My 5 1/2 year old is so incredibly shy that it's almost crippling.  I honestly don't know if something needs to be done or if I should just let it go and let her be.  We've always dealt with it as best as we knew how and thought she might grow out of it.  She won't speak or even look at people some times.  It's usually an ordeal each week when we take her to Sunday School (because there isn't a permanent teacher, so parents rotate teaching).  She has a hard time adjusting to change.  She even has issues with people she knows if she doesn't see them on a consistent basis.

I took her to her very first guitar lesson tonight, thinking she might prefer one one on interaction (since she doesn't seem to care for group activities).  She's also been asking to learn to play the guitar - and Santa brought her one for Christmas.  Anyway, she would not speak to her teacher the entire class.  She spent a third of it in tears not wanting to even look at him.  She's always had a hard time talking to people - kids, too, not just adults.  I'm glad that she's cautious and doesn't talk to total strangers, but at what point is it disrespectful?!  She won't answer when spoken to or anything.  But, what can I do?  Seriously, I can't pull the words out of her mouth!

I thought we made some progress - and in some regards we have.  There was a time she would rather go without than have to ask someone for it.  So, one day at McDonald's she asked a person for more barbecue sauce and we were thrilled.  That was a huge deal!  We've had several more instances like that in recent months, but deals like today make me feel like we've taken a big step back.  

Any advice would be greatly appreciated!!