I feel like the narrator of this song is an unreliable narrator, & that John should probably be worried about the flirting of his (apparently bisexual) lover.
Then again, I also think that woman on the "Jake from State Farm" commercial has probably caught her husband making illicit middle-of-the-night booty calls before, & has every right to be suspicious. So maybe I'm the suspicious one here.
(This is the good version, not the weird saxophone version. Don't get me wrong, I love saxophone - used to play it myself - but this one is better. Heh.)