My friend has been dating her boyfriend for 2 years and has never spoken to his sister but are now on facebook?

[Jazz]

ANyway so the guy hasnt told his parents, but his sister knew about the relationship. However his girlfriend who is my friend finally decided to make an effort to talk to her and added her on facebook. She doesnt know what to say though because they have basically never spoken. How should she write on her wall casually but show that she is slightly making an effort?
Its been 2 yrs so its awkward but obviously both know of each other. The sister is older than the girlfriend, both are succesful.

[Ami L]

Something like

"Hey, I just realised I've been seeing _____ (Bf's name) for 2 years now and have never really gotten to know you and the rest of his family. How are you?"