Delete All contacts on Icloud

My wife was testing my old iphone to decide if she wanted one herself. All of my contacts were upoaded to her old mobile me. She got her own phone and has now switched to Icloud. All of her contacts on her MAC merged with my old ones. How can I delete everything that is on the cloud and refresh with only her contact list.

Need to make sure I dont lose her contacs on the MAC.

Thanks in advace for your help.