It's difficult to un-do one of these situations once it
has reached this point.

Unfortunately, once a woman has "made up her mind" about
a guy, it's usually VERY difficult to change that mind.

If you're in a situation like this where a woman has
said "I only like you as a friend", then you're best off
going out and meeting some other women, and getting on
with your life IMMEDIATLY! Don't wait. Get on with it.

If you disappear from HER life, then turn up a month
or two later... and you're dating a few other attractive
women... she might see you in a new light.

Jealousy is a VERY powerful motivator to women, and
this is often what it takes to get a woman to see you in
a new light once you've let out your INNER-WUSSY too early
in the game.

Point: Don't try to un-do it. Just get on with your
life and quit obsessing over her.