confused again

Well here I am, confused again. I'll explain. Yesterday my wife called and was real nice on the phone, then she asked if I could watch our daughter for a few hours in the evening because she had a study group for one of her classes. Thats cool. I get to see my daughter for a few hours. So she says she will bring her over about 6 or 6:30. Ok by me. about 5 she shows up to drop her off. Not a problem. She even made chicken and dumplings and brought them over for me to eat. Wow. Dinner and time with my daughter! On her way out she mentioned that our daughter still had to do her homework so I got her book out and looked at what she had to do. She failed a math test so she had extra work to do so that she could retake the test. She wasn't happy about having to do it. She was still working on it when her mom came to pick her up about 7:30. When I opened the door for my wife I could see that she had red eyes like she had been crying. OK. It hurts to see it, but as far as I know it isn't my business, so I didn't say anything about it. She wanted to talk to me in private so we went back to the bedroom and she started showing me what paperwork I had to fill out for the divorce. Yay. Then she started in on me about "taking back the jewelry" and how it wasn't very nice, etc. So I took the bait and started arguing with her. Then I figured out that what she wanted was to argue with me, so I just said "fine, it was." And dropped it. Took the wind out of her sails. So then she started on something else. I just walked out so that I wouldn't get into an argument with her. If she wants to argue with someone, she can call one of her "friends" and start something with them. So now I am wondering why she was crying and why did she try to start an argument with me?