It could be that Irene faked her death for a non-Moriarty reason and simply copied the MO of a well-known serial killer at the time, and Moriarty happened to find out about her. But that seems like at least one coincidence too many.

It'll be interesting to find out in the next episode if Irene's British or American (or, indeed, something else). Unless they mentioned it this week and I missed it.