Yes, I believe she was still living with him. But God only claimed fornication and adultery are sins, not living in the same house. When we use "living together" as a euphemism for having sex outside of marriage we are judging unrighteously. I think the best way would be for one of them to live somewhere else until they are married (It doesn't have to take THAT long to plan a wedding) if they can. But if that's not practical right now (financial reasons or whatever) we have to understand that we have no more right to assume they are sinning in their house by having sex anymore than we have the right to assume they are committing any other sin behind closed doors. We also have to remember that not living in the same house rarely prevents any couple from having sex together (whether in sin or not) when they want to.
Added: See Jason, more of the cop logic coming out!