P, I am so sorry that you are having this thrown at you, especially at this time of year when problems affect us all a lot more than they do at other times.
I think in both cases the people you are having problems with are ignoring their own behaviour and making out like you're the one with the problem. Whether you have kids or not is irrelevant; your friend has rebuked what sounded like a really nice attempt on your part to make things better and your boss has gone back on your original agreement and didn't even have the guts to tell you himself. Both are trying to guilt trip you with the kids things which is pretty low. No doubt if you had kids that would have been used against you in much the same way; people like that will use anything they can so you can't win, no matter what.
If your friend doesn't want to be friends with you any more she could have just contacted you less and let it die out on its own or she could have told you straight that she doesn't enjoy your company like she used to and would rather not see you any more. Instead she throws a cheap shot at you which makes you feel like a demanding, petulant child - that's what she's aiming for. Your boss is doing the same thing; he knows your situation, arrangements have been made, he's remade those arrangements and tried to impose them on you, then makes you feel like he's doing you a massive favour by 'allowing' you to stick with your original arrangement and chucks in a guilt trip with it about your colleague needing to be with her children. If it's that big a deal for him he can pay a temp to come in for the day and cover for anyone that can't or won't work.
Jeez - I'm steaming now as well. These people are a**holes, P. I know that doesn't help much at the minute or make you feel any better but these are definitely unpleasant people to be around. It's so hard because we do seem to draw people like this to us and their comments and actions hurt so much because they're so reminiscent of the kind of c**p we had to deal with growing up.
On the positive side, you stood up to your boss, held your ground and refused to be swayed by his emotional blackmail - that's a really good thing. Your 'friend' doesn't deserve your friendship or the nice email you sent her.
Try and bear in mind that people like this will use any situation against you - if you did have kids you'd have got a load of 'the world doesn't revolve around you because you had a baby' type stuff. It's hard when people chuck stuff at you that you've no control over - I've had stuff thrown at me because of mental health problems in the past. It's hard to shrug it off but try to see that it's them with the problem, not you, and you've handled the whole situation really well.
Having children is no-one's business but your own. Deciding to have kids is your decision, no-one else's, and no-one is a better or worse person because of that. It's a cheap shot to throw and I hope that you get out of that job, and away from that friend, sooner rather than later.
Thinking of you, P, and hoping you will spoil yourself a bit and give yourself a big pat on the back for handling these morons as well as you have.
Twoapenny xx