I've heard the excuse and I don't believe it, and have said as much to Adam and ParisB.
Essentially she has made up another prossie (whose existence cannot be substantiated as she works the street and only advertises in the paper) who worked out of Paris' place for a bit and used her log-in to make those posts on mumsnet.
Even if that was true, are we really to believe that Paris only became aware of the posts after I started this thread? Would she not have wondered what all the mumsnetters, who were sending her pms, were on about? She could have had the posts deleted then.