How to tell a girl you like her...

[Inseriousity.]

Ignore kyle. he's wrong. very few people ask directly.
if she's given you the opportunity to come clean then grab it with both hands otherwise you'll have to awkwardly bring it up yourself.

[MilksAreUs]

What happens if it wrecks the friendship though?

[Ahnime]

You should probably give her some time first, once she's over him, you could just ask her if she has a moment. Just tell her how you honestly feel and if she feels the same way, that's great! (Sorry I'm not the best on advice!)

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What happens if it wrecks the friendship though?

It won't, it might be awkward at first but if both of you want to be friends one way or another one of you will make it happen. If you truly value your friendship, you guys will stay strong.