I would have already termed.
Have you warned them? I mean, do they KNOW that you are not happy with EVERYTHING you listed? I haD a tendency to down play how upset I get with dcp's and then my dh pointed out "Well, duh, if they don't know all of your nice notices and newsletters mean NOTHING." So I have actually said to dcp's "This is unacceptable and will not be tolerated." on NUMEROUS occassions.
If they have been sufficiently warned, and you have spoken to them A ND given them written warnings, etc then absolutely term.
I would be willing to bet this dcp disregards your policies either bc thinks that they don't apply to her with a past personal relationship or that she doesn't understand that she is on thin ice.