I’m sorry, but I disagree with those here saying things like “it’s the wife’s problem, she’s just being jealous” etc etc. The fact that you’re putting their business all over the Internet is a line that you have no problem crossing. I would be uncomfortable in that position myself. That’s not your husband, it’s hers. And the dynamics of their relationship are theirs to sort out. It’s also on your friend to decide whether he wants to be married to her or not. Obviously she’s not okay with her husband planning trips to the cinema with another woman behind her back (he didn’t tell her, so it was behind her back, whatever way you dress it up), so as her husband he should either respect that or leave.
If my husband took another woman to the cinema without telling me, I’d be upset. Because it comes off as high-handed and deliberately cuts her out of being able to voice any objections or concerns. Which shows a total lack of respect for her feelings, while at the same time showing lots for how you’re feeling. I wouldn’t like it either. He doesn’t appear to be taking his wife’s feelings into consideration. Maybe that’s why she went nuts about it. You don’t either, but it’s not your job to.
Bottom line, no matter who you are, that’s his wife. If she’s uncomfortable with something, like I already said, he should either respect it, or leave her. Putting her in a position of having to accept something or be called horrible all over the Internet AND national newspapers by you - that’s just wrong. If I was her, I’d have left him.
The dynamics are different now that your husband isn’t a buffer. I’m very sorry for the loss you’ve suffered. Maybe she feels uncomfortable about the amount of time he spends alone with you now because she’s concerned that maybe grief will make you both grow closer than you would have previously. It does happen. It happens a lot.
I wouldn’t be comfortable with my husband spending a lot of alone time that excludes me with another woman. If he wanted to go see something and I didn’t, then he said “okay, well is it alright if I bring my friend instead? I want to see it and I think it might cheer her up a little” I’d probably be okay with that, but him arranging something that actively cut me out? I’d be upset. It would make me wonder why they both felt the need to keep it from me until after it happened. We’re all human. And given his attitude towards her, I wouldn’t blame her for feeling a bit insecure. Maybe her telling you about this stuff was her way of asking you to back off a little? She’s clearly not happy with the situation. Both of you should respect that.