Sally: "Yes, it's been a rather tense week for me. ImaginIt, you know.""
"You know" here means that Sally wants to discuss a subject both people know about, so she just has to give one word (ImaginIt) to describe the situation.

Ivan: "At least you didn't crack. I think I would have sold on Tuesday, and taken the loss."
Here Ivan is complimenting Sally for staying cool in a difficult situation.

Sally: "If I had been sensible, I would have too. I was lucky."
Sally does not think she was lucky, but she does not want to suggest that Ivan would have been stupid so sell, so her reply is diplomatic.

Ivan: "Really? I thought you had faith in the company. After all, you brought a lot of shares on Wednesday."
"Really?" here shows that Ivan does not believe Sally when she says she was lucky. He points out that Sally brought a lot of shares when the price was lowest.

Sally: "I was hoping for a bounce. And fortunately it came. So I unloaded and cashed in this afternoon. I can spend the weekend with my mind at rest."
Now Sally accept Ivan's praise of her work. But she indicates that now she wants to finish talking about this topic.

Ivan: "Nice work. How's the rest of your portfolio?"
Ivan takes Sally's suggestion, and widens the subject.

Sally: "Nosy. Ticking over. Most of my shares are long term holds, so I don't have the thrills and spills you and Peter have. Have you two made up yet?" Sally tells Ivan to mind his own business. This is done in a casual way that shows she is relaxed in his company. She dosn't want to discuss her portfolio, she wants to discuss Peter, so she links this with the previous topic.

Ivan: "Cold war, I'm afraid. His nose is well out of joint."
Having a "nose out of joint" means "offended and angry". A "cold war" is when people feel very hostile, but no not do anything obvious about it. Ivan does not show any sign that he is sorry, or that he wants to change this. "I'm afraid" is put in only because he knows Sally is not happy with the situation.

Sally: "It's a pity. I don't like having bad blood, it poisons the whole atmosphere. Well, there you have it."
"Bad blood" is when two people do not like each other. "Well, there you have it" means that Sally accepts the situation, and she is not blaming anyone, and as she sees Ivan is not going to help to make things better, she tells Ivan to change the subject again.

Ivan: "Indeed. Well, I would say let's put it all behind us for 48 hours, but I've got to go home to read up on some company reports."
Ivan tells Sally she is right by saying "Indeed". Then he changes the subject as Sally has suggested. He suggests his work as a topic.

Sally: "Wuffyburgers on your plate?"
This is a small joke. Having something "on your plate" is something you have to deal with. But Wuffyburgers are a type of food. Sally's answer also shows that she can tell what Ivan is thinking about.

Ivan: "Yes. The shares have gone up nicely. Now I have to decide whether to hold or sell."
Ivan wants to say that he has done some clever dealing too. At the same time, he respects Sally's opinion, and he would like her advice.