Debunk the "Murder Mystery" email

I’ve just received the email below for the third time. I am relatively sure that it is an old puzzle of the “lateral logic” type. But my friend says that the claim at the bottom of the email is 100% true. Can you help me debunk it? I glanced at snopes but didn’t find it (but did not search hard.) Here is the email in its entirety, including the claim:

Here’s what Snopes has to say:

http://www.snopes.com/inboxer/hoaxes/sister.htm

Damn, you beat me to it. But to save our OP the effort of clicking a link- no, it’s an UL. :dubious: