Alex doesn’t get it, at first.
The way Maggie tightens her jaw and bristles and comments about running buddies and super skirts and hasn’t anyone let Supergirl know how much property damage she causes on her rescue missions?
She doesn’t get it, because Maggie isn’t one of those people who hates aliens on principle. The opposite, in fact.
It’s Winn who breaks it to her.
“Alex. Alex. She’s jealous.”
“Of what?” she splutters, nearly choking on her beer.
“Well I would be, too, you know, if my girlfriend was all over Supergirl the way you’re all over Kara and I didn’t know you were sisters.”
Alex pffts and Alex shakes her head and then Alex’s eyes fly wide. “Oh my god, she’s jealous.”
And she is.
Because yes, she and Alex have a shorthand, but Supergirl knew her first and – she hates admitting it – the damn superhero knows her better.
And suddenly it makes sense – yes, the bristling and the side comments and the smarms – but also the way Maggie will hold her closer, fuck her harder, kiss her deeper, pour more of her soul into her, on the nights that punctuate the days they’ve jointly worked with the pretty blonde who touches Alex and makes Alex laugh and looks at her with those blue eyes that Maggie is convinced must be more beautiful to Alex than her brown ones.
Alex can’t tell her – not yet, not without the okay from Kara – but she starts holding her hand more. Around Supergirl. Starts calling her babe more. Around Supergirl. Starts kissing her. Around Supergirl.
Which drives J’onn absolutely up a wall, because so often, whenever the two of them are around Supergirl, they’re around J’onn, too.
“Just tell her already,” he implores one night. “If I have to see my daughter… being romantic with her girlfriend in the field one more time I might just surrender my position.”
Kara overhears and Kara laughs and Kara tells Maggie and Maggie’s eyes fly wide and everything makes sense and she doesn’t stop kissing Alex until J’onn clears his throat for the thirteenth time and they’re both weak in the knees and breathless and so, so securely each other’s.