I think the issue is this.
I am also a "busy working mother". I don't have a chubby baby anymore. In fact, neither of them were ever chubby, so perhaps I'm not qualified to speak anyway... but I do have 2 children.
I never go to the bank any more and my bank is not convenient to me. On the very rare occasions I go into the town, I still don't go anywhere near the bank and quite often forget to go up there if I have a pesky cheque to deposit. And end up having to go back.
I completely get all of the issues around the inconvenience. It is tricky to fit it all in, find the time to shop for something, buy something that is worthy of a gift to report back about...
Many of us are in the same position.
However...
When someone used to send me a cheque for my birthday, I made sure that I thanked them and then wrote/called to tell them what I'd spent the money on.
If I had forgotten because I'd got caught up in life and had to be chased to find out what I'd bought (only because the giver hopes you've bought something nice) I'd have had the good grace to feel guilty about that and not be so egocentric that I could still only see it from my own perspective.
Are you unreasonable for being hurt by what she said? Yes. Because you were in the wrong, you hurt her feelings, she felt ashamed that her gift hadn't been respected regardless of its value and when you were pulled up on it, rather than apologise and just accept it, you came on here and demanded sympathy and understanding for your own hurt feelings.