She was probably either at her house with Jagger, or out with someone too... they've been divorced for a while now. They were back together, just not married, for a while; but last I heard, they're no longer a couple. But even if they ARE back together again, the article didn't say if Scott and Kristy were there as a couple, or just there together. There's no rule against hanging out with friends, even of the opposite sex, if you're in a relationship, right?