How can I confront a horrible person at work?

I've always gotten on quite well with my colleagues, well so I thought I did, but recently I've found out that one colleague has been bad mouthing me to my other colleagues and my boss for no reason. She's told my boss she thinks I do nothing (which is ridiculous, and obviously he does not also think that or I would be gone) but the fact is that I feel bullied and undermined by this person. What can I do? I was considering putting in a complaint about her but how do I go about this? Please help! Any help would really be appreciated.