Man... I think you were in way too deep that day when you saw her. Your shyness was due to your fear of rejection, you had too much intent to begin with. Imagine if you just walked up to her with no intention on scoring with her, that nothing-to-lose attitude is going to get you quite far from my experience. It's just like your first day at a new school, you just naturally talk to those people sitting around you.
Think of it like this. Every girl you meet from this point onwards, will either be hot and doable or have friends who are hot and doable. Talk to every girl, if they are good, have a go, if not, move on to their friends. There are too many pretty girls in this world for you to drown in sorrow from this failure. Now go out there and get them all!!
There is a lot of truth in what Brian is saying (sounds like a counsellor/psycholgist talking!!!).
Before I start I should preface this by saying looks aren't everything...I should know!!! Don't overthink the situation...make sure you're not already "married with kids" before you start talking!!! Everyone assumes that the "hot chick" has a boyfriend (or are intimidiated by her looks)...NEVER ASSUME!!! Most of the time they are just waiting for someone to talk to them and find out who they really are....just have confidence in yourself (be yourself) and never think "why would she want to be with me??" (That will work itself out in time!!)
I reckon this is why you see often see absolute D#@*heads with "hot girls" ...they've really got nothing to lose and most don't lack confidence.
If your problem persists you should watch 40 Year Old Virgin for further advice!!!
I have friend who is like way worse that. The poor guy hasn't had a real g/f before and he is 21 this year. We were at a pool parlour one time and there was a looker by herself at the table across from us. I told him he should go over and offer a challenge, but he declined, so to encourage him I said I'd pay him $20 to go over. He never did and he knew he blew a reasonable opportunity; I spose I didn't make it any better by hecling all the way homer either . Ironically his name is Andrew too...
My advice has been pretty much covered by everyone else here. Build up some dutch courage and just do it before you start to overanalyse what you should say etc. The longer you wait the harder it becomes.
I think everything's been pretty much covered but i had the same problem in my teens, not being able to talk to hot chicks. Cured it quickly tho, started walking up to random stranger chicks who i wasn't attracted to and struck up conversations. Before long i trained my mind to pretend the hotties were ugly thus making it a piece of cake. I guess it's like the whole public speaking thing and imagining every1 in the audience is naked (the imagining hot chicks were ugly saved me a lot of embarassment with that 1 too). lol