I can't see that, in association with tart-making, there's anything sentimental about the phrase Queen of Hearts. Forget the Princess Diana stuff which may gets in the way of the phrase for a lot of people these days. (And note it's not "queen of my heart" - making it "of hearts" has quite different associations.)

I know it's easy to use the term ironic to get away with anything, but in this context I definitely think there's an ironic tinge to it. Sardonic too. And that goes double for the last line, which I'd definitely read as having a self-mocking colouring.