What’s it mean when my wife is not truthful about..

My wife and I are on the verge of divorce, she has been talking to other men and one of them happens to be a guy that we argued about multiple times during our relationship because this was a friend of hers growing up, but they dated in their younger years. He always liked her, but she says he’s not attractive and she will never give him the time of day. Now that we are here and she wants a divorce. She immediately started talking with him again and claims that there is nothing between them. She had went to go see him in another state over the weekend and he paid for her flight. She lied and told me that it was for Work. Then when I kept asking here about it she finally said she seen him and said they did not have sex in a very hostile tone. She has slept with other men but for some reason whenever I talked about this particular guy it triggers her idk why. Anyway the crazy thing is after she came back from that trip she comes to my door and gives me the divorce papers she has been hesitant to give me for awhile, and also after talking to here about dating him she says expect the worst never say never… so it went from never to never say never….so my question is..why is she so hostile toward me and then , do you think they had sex and that played a part in her coming to my door with the papers? I feel like something’s has changed after seeing home out there, for 2 days.