How to deal with a "snake?"?

This weekend, I have to attend a work conference out of town. Everything has been paid for, and my workplace is counting on my going. This morning, however, I found out that the person I am going with has been undermining me at work. The problem is, I found out about this surreptitiously (a forwarded email from another colleague) who thought I "needed to know" that this person "was not my friend." Now, I am in a predicament. I am very angry with the "snake," yet am in a situation that will look bad on me if I "get the flu" and back out. How can I coexist with the "snake" all weekend? (And, yes, we have to share a room...company savings, you know!) Thanks!