Space Jam Confirmed
I would never do this as DM. In this instance the DM set the stage for "metagaming" to occur and some DMs would then demand the players don't "metagame" in the face of that. Changing things to thwart the very "metagaming" the DM encouraged is not the way to go in my view. The problem - if it can even be called a problem - is easier solved upstream by reminding the players that assumptions can be wrong and that the smart play is to verify one's assumptions before acting on them.
The DM did not necessarily "set the stage" for metagaming in this instance. The character in question is obscure enough that the DM could easily have been totally unaware that she was a pre-existing character not original to the adventure, and have no way of knowing that a player would know who she is. The DESIGNER set the stage for metagaming, which is why I question the designer using this character in this way.