How do I handle disingenuous behavior?

I have good reasons not to trust my mother-in-law. I do my best to handle this by having a polite but distant relationship. I've never said anything negative to her, but she is constantly sucking up to me even though I know she disrespects me behind my back. She's very manipulative and needs a lot of attention. My pregnancy has made her so extra. I try to answer her politely, but I'm aware it comes off as short and cold, which I don't like being. I don't want to have any heart-to-heart conversation with her because she is just not a genuine person and she's very manipulative, so I know it won't go anywhere (I gave that a try about 5 years ago). She always talks about how much she loves me when I know she doesn't, and I firmly believe that respect is more important than love in most situations. What can I do to make her back off?