I've never been in such a situation so all I can recommend is you have an interment and open discussion with that person. Try to be nice and agree with whatever he/she says unless of course it's too uncomfortable in which case say nothing. Be apologetic up to a point. Just explain you want to be friends again. If appropriate explain your action was meant to be with good intentions, and why. Also, if appropriate find out if that person has a problem and likes to discuss it with you. Try to help as much as possible. I wouldn't discuss the reasons why he/she went behind your back and spread the rumours. Let him/her do it. Good luck.
