Well, the present perfect here has the sense of action in the past that has an effect or relevance continuing into the present, which is its standard use (or one of them, anyway). But what you say seems reasonable: in this context it might well be a cue for the guest to start making her "special goodbye".
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BamtoriYou've come to say a special goodbye.Almost exactly: You are here for a certain purpose: to say a special goodbye.