My answer would be: It depends.
If there is a question of something dire could happen to your friend: illegal activities; rampant substance abuse; toxic environment; then yes, tell her.
Otherwise, if she mentions the possibility to you, and you say, "Oh, yes, I know that office!" in a bland way, then you wait for your cue. People who truly are unaware of potential bad things will pounce on this: "Oh, good! What do you know about the place?"
But if that hint just lies there, let it lie.
WARNING: if you do this, you must truly lay the hint out in a very bland manner. You can NOT wiggle your eyebrows or widen your eyes. You do not want to poison your friend beforehand unnecessarily.