I kind of give Seiya a pass since she's basically a teenage girl living in a male body on another planet...or possibly she could even be a milleniums-year-old alien ...who knows?
But her behavior is not attractive either as Kou Seiya or Star Fighter.
The anime tries to play it off that she's just being supportive of Usagi, and to some extent, that's true.
But she's also creepy, manipulative, and also knows she's not available and comes off as someone wanting to get their kicks while in town then get out when it's convenient.
I think she does come to care for Usagi genuinely, but she almost made Usagi a wreck. In some ways, I do think Usagi needed Seiya, she wasn't opening up to her friends and when Seiya threw that rose, Usagi finally broke down, like she needed to, so she could heal.
But then she just had to ask: "Am I not enough?"
No, Seiya! She's hurt, confused and you just come barging in thinking because you're cute you can fix it all.
It reminds me of how abusive Haruka is in the manga. Even if Neptune isn't upset, it's disrespectful to her and straight-up cruel to Usagi.