Why she took this upon herself I have no idea but reading this, she is an embarrassment. That would never have happened where I work, never.
Having dealt with some of these types, I would bet she took it upon herself
to show off. A la: "Look at ME!
I did all this extra stuff that Peaches didn't think of!
I went above and beyond!"
All the policies and meetings and clear communication and whatever else won't do a thing with this type of person until her boss decides to reign her in (and get the credit card away from her). You know the old song "Fun fun fun 'till her Daddy takes the T-bird away....."