I understand you are feeling surprised by the development, and thus hurt. However, that doesn't necessarily mean that there has been an intent to hurt you. To be honest, it doesn't sound like she did anything wrong here. He could maybe have been more considerate, though. It's a bit unclear how clearly you've actually communicated with your husband, and if there's just been misunderstandings or actual violations of agreements.
Since (I assume) she doesn't know about your agreements with your husband, she doesn't know you want to know the people he dates, and doesn't know you feel she shouldn't make out with him unless you have gotten to know each other. And you blame her that when you met her she didn't make an effort to get to know you; yet it doesn't sound like you made an effort to get to know her, either.
On to his behaviour.
Originally Posted by gwendolenthefair
I expected he'd be gone an hour, perhaps two, and I assumed that he and I would do something as a family with our children, after his return. I myself try never to spend weekend time away from my family, I only very rarely do so, and then only with a very established partner.
I sounds like you have certain values about how weekend time should be spent: preferably with family, and if a longer time is spent with another partner it should only happen with an established one. Have you communicated these things to him, and asked how he feels about it? I understand you are feeling that he placed her above your family time, but he may not know this, and propably doesn't since you write you assumed
he'd be back in 1-2 hours rather than that you told
him you'd want that.
However, I'm quite confused with the making out and all that. He knows that you want to know the person before they start to date. It seems that maybe you two have a different definition of "dating", and need to be more clear in communicating about the boundaries. It sounds like he feels that since they aren't dating he did nothing wrong; and also maybe that since you've seen her she's not a total stranger? And you feel that you'd like to know a person better before he makes out with her, even if he doesn't consider it dating? If he doesn't want to date her, does he want something more casual (I don't know what that would be to him, friends with benefits..)? Would you be ok with that? You should talk and try to be as specific and clear about what each of you want (in this situation and in general) as you can.