Hi PianoDood,
I would guess that your wife initially got confused over who was supposed to be phoning whom.
first, it was my fault that I didn't call her last night even though she had specifically said she would call me after dinner. I waiting for her.
If she thought you were supposed to be calling her and then you didn't, that probably triggered her fears of abandonment and she probably spent the evening ruminating on why you didn't want to talk to her. When the two of you spoke and you asked why she didn't call, she was probably quite embarrassed remembering the things she'd been thinking and feeling last night when she was waiting for you to call.
Once she realised it was a simple misunderstanding, her immediate reaction was to deflect from her feelings of embarrassment, plus the feelings from last night probably didn't disappear in the instant that she realised she'd been mistaken - it probably took a while for her to take reassurance from the recognition that it had been a simple misunderstanding.
By the time she got off work and called back, she'd had time to process what had happened and get her emotions regulated. At this point, she was probably able to feel
relief (instead of embarrassment) over the fact that the lack of a phone call last night had just been a simple misunderstanding and hadn't meant you were rejecting or abandoning her after all. Which is probably why she switched to an upbeat and cheerful mood, because a weight fell off her shoulders once she got her head round what had happened.
That's my guess. What do you think?