I try to avoid shopping while hungry as I make bad decisions but I wasn't expecting we'd be dropping by the store when my wife and I were out on a walk. She asked if I intended to share with our kids the big bag of chips I'd picked off the shelf (not wanting any herself). Well, no, my stomach was doing the thinking and I had intended to eat that entire bag, but coming to my senses somewhat I decided half would satisfy my craving and the kids could have the rest. To that end I chose a different bag, telling my wife a less popular flavour would help ensure I'd have more for myself. Sounds selfish, I know, but my adult son eats snacks as meal replacements and there have been many occasions when I went to get a snack from the pantry or freezer only to find he'd already eaten everything. As he pays room and board I usually don't have a problem with him getting his portion, it's just that he's incapable of pacing himself and ensuring everyone else gets their portion too.
This isn't news to my wife who previously had hidden a box of popsicles in the meat freezer instead of the snack freezer for exactly this reason (which worked well as my wife, daughter, and I snacked on popsicles over the course of two weeks instead of the typical few days).
After we got home, I opened the chip bag and left it out for sharing. My son was playing video games and didn't notice the bag right away, but my daughter had some and as I was still hungry I quickly ate my portion. This prompted my wife to laugh when she entered the room and exclaim, "the bag's already half gone! So much for your plan to get chips that no one else likes!"
The kids didn't say anything but I was mortified that she had shared what to me had been a private communication between us (and one that -- on the face of it -- doesn't paint me in a flattering light). I approached her about it in private later and she told me she hadn't considered it a secret, that she'd directed the comment at me (meaning, I suppose, that she wasn't purposefully trying to embarrass me), and that I was blowing things out of proportion and neither of our kids cared about this as much as I do.
When I asked her how she would feel if I told our son that she had hidden popsicles because she didn't want to share them with him (which to me is equivalent), she said that wouldn't bother her at all. Finally, she told me she was sorry if I felt embarrassed but she feels she has done nothing wrong. That's not satisfying as my feelings are my own and no one needs to apologize for them.
She feels this was a non-event, and while the event itself is relatively minor to me the bigger issue is that I am unable to make her appreciate that it still feels like a small betrayal.
What steps can I take to better explain to her why I see this as a betrayal of our trust?