Drug Testing & Girlfriend?

So I'm gonna be taking a drug test soon (probably next week). I do not use drugs (actually, I don't even drink). However, my girlfriend recently experimented with some pot. I have read that proximity to people using can cause a false positive for THC. What does it mean by proximity? Obviously this is a stupid question, but could bodily contact (such as say, a kiss or ual activity) the day after she used cause a false positive for me? Is that enough proximity or do I need to be present when she's using to create a false positive? This is probably a really stupid question, but I'm quite concerned because I'm applying to be a Police Officer and I would hate to have the embaressment of a positive test because of something as insignificant as a kiss. Any words of wisdom?