this might be something that just happens in general unfortunately, where people tend to (most of the time unconsciously) give the "better" characterization to the one in the pairing they favor more. i think a good way to try and combat this is to write from both povs!! within the same fic or just in different fics. even when you aren't writing one character's pov, it's still very important to consider how they are thinking about and reacting to the events of the story since it guides their interactions with the main character