I'm not saying it's NOT someone c-list, but I don't think her notting Sienna was any kind of clue as to the person's identity. She didn't "not" her as part of the blind; she just happened to have a Sienna pregnancy story soon after posting the blind and said "p.s. - she is not the subject of When She Conceived." I think it was just a preemptive measure to stop people from thinking the story was a clue.I'm thinking we may be aiming too high if Lainey's notted Sienna Miller. It has to be someone a bit more C-list
I'm still on my Salma train but I also like the Beckinsale guess above. Lainey's always going on about how over-dressed she is, which could equate to wanting to be desired, and she gets lots of work from her husband.