Why do we feel jealous of fictional characters?

It's a rather strange situation, but what happens is that a person in a romantic relationship can become jealous of a fictional character, specifically if their partner has a crush on that character. But why?

But imagine being in a romantic relationship or perhaps feeling attracted to someone, and that person has a crush on a character who is the complete opposite of you, and who might even be better than you. It hurts, doesn't it? You try not to let it affect you because "it's not real," but you feel inadequate for not meeting certain expectations.

For me, constantly hearing "aww, she's so cute" or "My wife" about every damn fictional girl whose main characteristic is being sweet and feminine is FED UP. It genuinely infuriates me to hear it because I'm the opposite, and I feel like I don't fit certain tastes reflected in those characters.

(Only I'm not commenting because I don't have the right to say so).

It's usually because, in my experience, I "fall in love" with VERY SPECIFIC characters, who carry an emotional weight and with whom I identify. I value attraction immensely; for me, it's not just any old thing.

Sometimes I hear talks about a kind of insecurity that borders on toxicity, which is unacceptable because it's still fiction.

For me, jealousy is understandable, but becoming unable to distinguish fiction from reality leads to many problems.