Sounds like a rough place to work! UGH!

My feeling is that you have 2 options, sit with the owner & the person that you are having conflict with to work it out until it's actually resolved and not before. Given her tract record (sleeping around and being a gossip), it sounds like this isn't really possible with her. Your other option, which is what I would most likely do, is to ignore her. Continue doing what you're doing. Be nice to her and to everyone else and don't fret about what she's doing. I can't imagine anyone believes her when she talks, I sure wouldn't. You have to be careful about the company you keep and if people are going to stand in a parking lot and gossip about someone, that doesn't say much about them.

Chip up!