My [27M] girlfriend [27F] won't stop swapping out my real groceries with small versions of branded items

It's basically what the title says - but the weird part is she won't ever admit that it's her? She just sort of looks at me and pretends to be confused when I confront her?
Basically, every few weeks I come home and some of my groceries are missing and replaced my miniature plastic versions of themselves. Come home from work and looking forwards to a coca cola?
Oh great, my coca cola is gone and there's a miniature plastic version. Break something small and need to tape it back together? Oh good, miniature duct-tape. Make eggs and want some tabasco? Oh great, miniature tabasco. You get the point - kind of funny, but pretty annoying too.
So far all fair play, clearly my girlfriend thinks its some sort of funny prank or practical joke, but the thing thats weirding me out is that she never acknowledges that its her? Even when I start to get genuinely upset, or frustrated she insists that its "so strange" that "random objects are shrinking in our home"?
This all culminated to last night... Last night I came home and I had been craving something sweet all day. So I started baking blueberry muffins - my genuine favorite treat for myself. I get everything together, preheat the oven, and I'm about to start making the batter when I open the cabinet and oh look - the flour is gone and replaced with a miniature bag of flour.
"Ha ha, so funny", I immediately call her and ask her where she put it but she keeps playing dumb??? I start making a slightly bigger deal about it I'm like "look, I went to the store to get fresh blueberries, I've been looking forwards to this, can you please tell me where the flour is?". She won't drop the act? Like what the hell??? Before we ended the call she slyly dropped "as if you need more muffins" and hung up??? Like what the hell.
I haven't called her back yet - so we haven't talked in over a day. I'm pretty mad at her over this - I went way out of my way to do something special for myself and she wouldnt drop the act when I made it clear I was genuinely upset.
Dating.mobi, I know this sounds insane, but I'm genuinely considering time apart over this. She clearly doesn't take my needs seriously. Do you guys think this might be breakup territory? Thanks for anyone's tips.
TL;DR; : Items from around my house such as sugar, a bottle of coca cola, etc "randomly" shrink into miniature plastic toy versions of themselves. My girlfriend won't f***ing stop and I'm losing it - she ruined my muffins to stick with this stupid joke.


Source.