I think I can understand the heart classpecting theory because she's very torn up about the name and her origins, namely her identity as a person. She's a literal plot contrivance made to make people angry and I could see that her deciding to love herself anyways despite a lot of people not liking her, making her a heart player since Heart players tend to be "self-absorbed" but I think in the case of Yiffy it'd be less her caring only about herself or whatever, and only being able to look at her relationships with other people through the lens that she's an inconvenience and not "supposed to be here" essentially.

But we haven't even really seen a lot from her outside of these forums (if you try to name yourself Yiffy or any of her names when you sign up for FRAF you actually get dialogue from her which is cool!) And the description for the Heart aspect really does match up a little with the way things are going now if you think about it in that way.