Simon..

I'd say take a chance..BUT with the mind set of not expecting too much up front. What I mean by this..is to maybe take things a little at a time..not to just dive right in and start dating her..maybe ask her out for coffee just as friends so you can get to know each other better..instead of the stress of an actual date..and you feeling that you might be shot down and rejected. Let her get to know the "REAL" Simon..the one that we all see here..and TRUST me, if this girl is smart..she won't let you get away!
As for her being outgoing and you not..some girls really like that..You just never know..and you won't know unless you take that chance and find out..but with every risk is the possability of hurt and rejection..yes, this is part of life and struggles..its sucks..but it is what sets us up and makes us stronger and better for when the right person comes along!
Simon..if you like this girl..then take that chance.. You just never know what might happen unless you do ask..and if you don't you might always wonder what might have been....(((HUGS)))) and good luck!