You will not know until you try. This might be The Day she checks FB. I don't know about involving the sister. It isn't totally out of the question. You could FB message the sister something like "I need to get in touch with (OMW's name). Would you please ask her to check her FB acct? Thx." That way you're alerting OMW to the message w/o spilling the beans all over the place.
Greek


Me45 H46
T25 M22
S21 & 19
D13
Separated and filed 8/08
Moved home 11/08



Happily ever after is one day at a time.