JustCrushed, I am so sorry mate. I have lived this, bought the T-shirt and signed up for the monthly subscription. It's terrible, and I know the panic you are feeling. From the get go, I need you to hear me very well: NONE OF THIS IS YOUR FAULT, OR BECAUSE OF ANY ACTION ON YOUR BEHALF. She cheated because it excited her, and because the threat of discovery and the consequences thereof were overridden by the thrill she gets from deceiving you.
I am glad you found this site, it is a godsend, and I am forever grateful for the care and advice I got when I went through this (check out my thread in this forum if you want a read, 'After 9 years of R....')
A few things stuck out straight off the bat,
a. Who actually starts a conference on a Sunday night? Sounds like she wanted some 'me' time in another city on a weekend (i.e Saturday night) I only say this because my ex-wife did the same.
b. What were the circumstances of her first divorce, per chance?
Just interesting points that made me wonder. Regardless, here's what I suggest.
First things first, you gather the evidence and print it out. You already had the smarts to clone the phone info, so it won't 'magically disappear' now. The fact she had no password on her phone shows how cavalier she was obviously getting, and how little she thought about getting caught.
Second, pack some bags for her and have them waiting when she gets back. You've done the financial bit, but if you do go down the D route, consider that she may have been using family money to book hotels etc etc. from what I understand of the US legal system (I am an Aussie btw), you can get this money back as part of any eventual settlement. Something to think about.
Thirdly, and I want to say this gently, you need to get STD tested. Not that you'll be of a mind to do so in any likelihood, but resist sleeping with her going forward. There is a phenomenon known as 'hysterical bonding' that some couples engage in once the affair is out in the open in an effort to 're-connect' with their partner. I digress slightly. Long story short, for whatever reason, part of the cheater's textbook is that they rarely like using protection. it adds to the thrill. Imagine my joy at discovering that my ex-wife's AP was a married polyamorist with two other girlfriends. How I managed to get a clear STD panel noting his cascading family tree of sexual partners still amazes me. You need to protect yourself accordingly.
On confrontation, give her the opportunity to confess. I am guessing you have a pretty good idea of the terrible debacle from her text log, but tell her that she has one chance to come clean and tell you what is going on. She will 99.9% lie and obfuscate, with an attempt to gaslight you and/or downplay the situation. 'He's only a good friend', 'the conversations are just sill sexual conversations that mean nothing because we are such good friends'...you'll likely hear variations of that prior to denying he even exists.
What will follow will be a series of 'trickle truths' i.e. she will only confess or tell you what she thinks you already know. tell her that you know the truth, and if she wants to save the marriage, she will confess to everything. One lie, you get up and walk.
My heart goes out to you mate. I've had this talk, I know how stressful it is. Remember: none of this is your fault.
Post confrontation, implement the Grey Rock method.