The cyber world is a world which allows our sub
conscious to take over, because this is a pseudo world, a
virtual reality.
Despite what most people say, the personality we present on the
Internet IS our personality. It is hidden in our
sub conscious, and is our truest personality. Well, that's
disregarding those who act as the opposite sex.
If she is more responsive on-line, that shows she is not as
comfortable with you, off-line. Physical proximity requires more
than just a friendly attitude - 70% of what we speak, comes not
from what we speak. It is how we speak, and our body
language.
Give her some time; some people warm up to strangers faster, while
others take a longer time to feel comfortable among newly-acquired
friends.