All good comments and appreciated. Part of my goal is to see how photographers interpret the narrative in my own words at face value. I know language is key whether written or oral. Nearly everyone has focused on a written contract, some even implying oral contracts aren't equally binding instead of just harder to prove. I see I need to clarify the following already if I take any action:
1. Most of the discussion above was written, although I incorrectly use the term "said". There were eight exchanges by email and one phone conversation, nothing face to face. I have used a lengthy written contract myself 99% of the time, including 5 years prior as an art director when I was hiring photographers before shooting professionally on my own. Ironically, I have advised this woman to start using written contracts with clients, but nearsighted in regard to myself. In each of the three cases I helped her, I did put basic wedding/event terms in writing by email, excepting copyright which is retained by the creator if no assignment is given. Keep in mind I'm mostly watching out for her vs. the client at that point (some ego invested).
2. Terms and time of payment were specified. I was to be paid the week prior at latest, but she used the "got lost in the mail + client's fault + I'm out of town" excuse after the fact. Certainly on me for watching it unfold and not bailing per terms. But there was the Catch-22 of the client already told I'm going to take care of them and looking so forward to meet me. The client did pay and admittedly she was smart to use the leverage of introduction, knowing I won't bail on them and risk my name.
3. In all cases like this, even a written contract does not stop intentional deception or playing parties off each other. For those who say no excuses for moving forward, maybe so, but 400 guests told you were a no-show is not good either. No one knows you are contractually in your right. The client only knows they paid.
4. I'm surprised no one has suggested I use the invoice and non-payment this long as proof of deception by the photographer. Or to act legally so that her client at least knows she is blaming them. In fact her phone message from Hawaii which I saved, says she didn't tell me when I'd be paid, but in fact is written. Two weeks have also gone by since her return. The client paid in full over a month ago. She just doesn't know I know that.
If you think you've a case and your attorney agrees, you're free to go to court. When I advised you to move forward my intention was to spare you a number of things:
1) Scandal. Don't know her and don't want to judge her; that being said, however, from her actions it's pretty obvious that someone who's been dealing as she has is quite shrewd and efficient at deception. She could manouevre you into a situation you won't be able to extricate yourself out of without surrendering a certain amount of uprightness. She could also slander you all across the social-media sphere and damage your business. If you've been caving in to her poor, overwhelmed, at-a-loss photographer pleas, wouldn't you think others would too? In the end you'll be the ogre and she the damsel in distress.
2) Vindictiveness. Whilst I certainly believe that she should be taught a lesson and stopped in her unwholesome practices, you, by virtue of being the offended party, could easily cross the boundary of rightful indignation and get lost in the land of self-avenging. This is never good, and deleterious to your physical and spiritual health.
3) Further headache. She's practically enslaved you into working for her through an underlying fear of a tarnished reputation and taking advantage of your caring about the needs of the clients. This has to stop. Besides, when it comes to clients, they really don't care about their purveyors' troubles, nor do they want to be dragged into a situation where they have to take sides or be called in to testify, whether in court or in informal quarters. I've clients tell me, in a clear tone of vexation, 'you guys figure it out!' All they want is their photos.
Again, if you think there's something actionable here feel free to proceed. Regardless of that, I still am very much of the opinion that you should sever all ties with her immediately.