Ivar Pawlus
Ivar Pawlus voted up Tom Jackson's answer

You can remind her of the possible consequences of her actions---including the potential trust issue---but anything coercive in nature would in fact be overstepping your boundaries (this is not an "emergency") and crossing hers.

Ivar Pawlus
Ivar Pawlus voted up Barb Cala's answer

All you can do is tell your friend you think she's making a mistake acting like that.  But you're not her parents.  They need to handle this.  You'll just become the "bad guy" if you get too involved in her problems.