@DahinOH
It's a confirmed PA (she admitted to kissing and groping), now let me ask you, if you're a single guy trying to have sex with a woman that allows you to kiss her, hold hands, touch her inner thigh, texts over 400 times in 11 days and sexts with you, why in the world wouldn't you just do the deed and have sex ? she's a grown woman, she deliberately hid their texts, put a woman's name on her phone, tried to keep you away from the party, etc..., again if your WW allowed OM all that why would he/they go for it ?
Your WW's story doesn't make any sense at all, she was actively pursuing this relationship, she didn't report his advances to HR, she CHOSE to cheat and got caught period. At this point I would be surprised if they hadn't had sex already, why stop at just kissing and touching ? why would a man alone with a woman who allows him all that and sexts with him not just have sex ? the answer, it's very unlike he would have stopped at just that.
By now you know cheaters lie and minimize, her response "I didn't kiss back" is total BS and straight fromt he "Cheater's Handbook", there's always more to the story.
Call her and tell her that if there's any chance at R, she needs to be completely honest with you now BEFORE you recover the deleted texts and that she will take a polygraph test to whatever is not in the texts. Here's a few questions you may consider she answers before you get the results and/or have her polygraphed:
1) You were cheating with OM and were sexting behind my back, you know this is BS, how many times did you make out with him and/or have any type of sexual contact including but not limited to BJs, HJs, fingering and/or fucking ?
2) Did you have unprotected sex with OM ?
3) Do you have feelings for OM and have you ever told him you loved him ?
4) You know your party story is BS and noone would believe you, what were your plans with OM for that night ?
5) Who else knew about your relationship at work or outside of work ?
6) Did you ever go to his house ?
7) Besides your lunches together did you ever meet him outside of work ? if so how often ?
8) Besides the A with OM, have you ever had an A or any inappropriate relationship with anybody else since we started dating ? if so how many and when ?
If you ultimately decide to give her the gift of R (you don't have to), have her read "Not Just Friends" by Shirley Glass, you can download it and have her go to IC to find out her "whys", don't waste your money on MC now.
Finally consult a D attorney to know your legal options and at the very least have her sign a post-nup in your favor in case you eventually decide to D.