Telling and not telling

I've told a few people at work, mainly my boss, and three of my co-workers. Two of those co-workers have been involved and supportive of my efforts to conceive and both have had difficulties of their own, either getting pregnant or during their pregnancy. The other co-worker is the guy that is in the cube next to me (so he hears all my one conversations) and basically, he's just about the nicest guy I know. And I trust him. And, being the only guy in a group of women he hears far more than I'm sure he wants to know.

Just a little background on the company I work for. We have about 25 employees right now. I work for a smaller division of the larger organization that is made up of six employees (including me).

I have not told one of the women that is in my work group. This is for several reasons. 1) she's been rather nasty to me several times since last summer (it's a long story and I don't have time to go in to it right now, but basically her people skills suck). 2) We haven't spoken about anything personal in almost a year. 3) She's never had a single problem getting pregnant or during her pregnancies. 4) I don't trust her with something so emotional to me, especially if something goes wrong with this pregnancy.

So this morning, my boss came up to me and said she was thinking and that she thinks I need to tell her. That it's not fair that everyone else knows (meaning the four that I have told). She thinks this would be a good will gesture on my part and I should take the first step. I told her that I don't necessarily feel like being the better person with this. She isn't involved in my personal life and I don't feel like including her now. I will tell her when I'm ready to tell the rest of the office. Probably in two more weeks if things go well. I trust the people that I have already told, I don't trust her.

What do you guys think?