Casey used to do that. I lunged her in her snaffle bridle a couple times, with a converter strap - Poly Web Lunge Line Converter - Horse Tack - LuckyPony.com
And now she is great. Never lunge in a tomb thumb or any shank bits, best bit is a snaffle, you can get away with using a kimberwicke though. Just make sure your friend knows to be very gentle and don't do it on a routine.
Or, tell your friend to go out and buy a rope halter (or make one). They have a bit more leverage than a regular flat halter... When Casey was learning how to lunge and was being very naughty my instructor used some sort of headstall that looked like a bosal- but instead of reins, a lunge line tied on it..