I don't think it's Olivia. That would be too easy. I think it has something to do with the name Spaulding. I'm not sure exactly which one, but aren't they always behind something?
And MAYBE just MAYBE it is Ava. This is a soap opera right? It's possible that she has a dark side that we've never seen. I'm just waiting for the day she snaps and loses her mind. It's bound to happen.