While not western, I think Hibiki and Miku from Symphogear have my favorite superhero-girlfriend dynamic.
In comics, the girlfriend character usually only serves one of three roles: as a source of drama because she isn't in on the secret and the hero is keeping his cape life from her, as a source of drama as a damsel in distress, and to assure the audience that this guy who runs around in colorful tights and mostly hangs out with other muscly men isn't gay.
In Symphogear, Hibiki's job is to save the world. At first this is a secret from Miku, but only for like 3 episodes of the first season. After that, Miku has a dedicated role in the show: while Hibiki's job is to save the world, Miku's job is to save Hibiki. Miku isn't a fighter, but she keeps Hibiki grounded and helps her focus on what really matters instead of getting distracted by boring moral choices. And whenever Hibiki ends up getting possessed or mind controlled or something, Miku's voice alone is generally enough to get her to snap out of it because they're just that gay.
Miku doesn't have any powers, but that doesn't stop her from having an active role in Hibiki's superhero life and a useful role in the story, instead of being a distraction from the plot like most superhero girlfriends are.