She's meeting up with my boyfriend behind my back!?

[Jordan]

So one of my close frends added my boyfriend on facebook , she has never met him by the way, and she starts to talk to him,webcam him,flirt all that lot , but recently she's been planning on meeting him behind my back on tuesday they have more plans for the week but it is just them and its beginning to irritate me as she calls him "fit" and things like that.I've never really been like this with guys buti guess it is irritating me as they are meeting behind my back and I feel as if I'm paranoid about all this...
Do you think I'm overreacting?
Should I say something to her?
If so what should I say?