Hi,

If a girl is told by someone that you are really interested in her or she finds out by other means, how do proceed with her?

Are you not already on the back foot because she knows how interested you are?

Any advise is much appreciated

surprise her. Act like you're not.

Go talk to her and be honest. The longer you put off talking to her the bigger a pussy you'll look; go do it and don't beat around the bush. "So, *** told you I like you huh?" See how she reacts, ask her what she thinks about that and talk about getting together some time.
Think about it this way. Someone told her you like her, and you know this. You now have a choice to either go talk to her about it, or not. Only one is productive. If you choose not to go and find out if she likes you back, that is putting yourself on the back foot. Her knowing you like her is only half the equation. Grow some balls and do it.
That's fake. Not to mention not surprising, cos in his situation that's what most guys would do. She's expecting him to deny it but she doesn't want him to, not if she's into him anyway. She won't believe him if he denies it because this came from a third party... even if that's not the case and she does believe he isn't really interested, why play mind games anyway? Think about how silly that is... you act like you're not interested in the hopes that she will reveal her interest for you, then you DO tell the truth. In the long run this isn't going to be good for the relationship... if he plays mind games like this in order to elicit certain reactions from her instead of just being honest and forward then she will do the same with him. They should just be real with each other.