I'm sorry that you had to find us but glad you did. Your WW is now a proven cheater and liar, I can almost guarantee you this is the tip of the iceberg, they've been in touch for a long time, you caught them sexting and POSOM is local, so this likely a PA already, she was already talking to yet another guy about porn so she may be a SERIAL CHEATER. Do not offer R upfront, you first need to know as much as possible about the situation, so here's a few of the basics:
1) Full EXPOSURE, expose them with all family and close friends and of course OBS (Other Betrayed Spouse) if any, without warning (very important), exposure typically kills the "beautiful, exciting and romantic" aspects of an A and replaces them with pure shame and embarrassment, the more she hates teh A, the more she will have POSOM (s). Make sure you include both sets of parents (if alive).
2) She needs to send an NC FOREVER letter/text to both OMs, one that you approve and watch her hit "send", short and to the point (no sweet goodbyes), then block them everywhere including social media, emails, etc.
3)She needs to offer full on demand access to her phone and all electronic devices and passwords and also enable GPS tracking on her phone, no questions asked. Don't buy the typical "it's my privacy" bullshit, in a M there should not be such a thing, once you tie the not it becomes "our privacy" instead.
4) She needs to write a detailed written timeline of the A(s), make her read it out loud to you and tell her she would be subject to a polygraph, that this is her chance to come clean and that you will record her, that prevents her from changing her story later.
5) Demand she gets tested for STDs/STIs, you should too, they've already met, some STDs/STIs could be transmitted via saliva (kissing), even if she denies it, the walk of shame to the doctor's office helps with remorse and helps to drive home her huge betrayal.
6) She needs to go to IC with someone who specializes in infidelity to find out her "whys", forget MC for now, at this point it's typically a waste of time and money.
8) Consult a D attorney to know your options, while you're at it, ask about an enforceable postnuptial agreement in your favor in case she cheats again or at some point you decide this is/was a dealbreaker for you (no alimony, she doesn't touch your retirement).
If she refuses any of the above just file for D and have her served, you can always stop if she comes around and you decide to give her the gift of R, or NOT ! but either way you will be that much further ahead in your path out of infidelity. Others will chime in with more advice, keep posting frequently, the collective wisdom of SI could help you go through this difficult situation, we've literally "seen it" THOUSANDS of times here, every case is different but cheaters typically follow a similar script.