Alex ‘I’m going to jump off this tall ass building and assume my sister will catch me’ Danvers blurting out 'Marry me’ to her girlfriend is absolutely in character.
Alex goes HARD at everything in life, with the previous single exception of her love life. College-aged Alex went hard, throwing back shots and putting her life in a negative spiral. DEO recruit Alex goes hard, completely turning her life around and making herself indispensable. Hell, even now, when she’s essentially second in command behind J'onn, she’s still going hard and doing things like 'Thursday morning knife throwing practice’, which you know isn’t necessary, it’s just who Alex is (and the other DEO agents find it a little terrifying and intimidating, but it also motivates them to be BETTER, because if Alex Danvers is still pushing herself like this…). Sister Alex goes hardest of all. She was willing to die in a damn plane crash to avoid the risk of Kara exposing herself.
Anyway, the one area of her life she never went hard in, because it never previously made sense to her, was her love life. And now she’s found someone who fits perfectly into her world, and we think she wouldn’t go all out hard on that? Maggie gets her, knows about the DEO and Kara, doesn’t show a bit of jealously or desire to come between Alex’s relationship with Kara, they have similar likes and interests, of course Alex is going to grab onto that with both hands and ride it at full speed. Alex Danvers and Maggie Sawyer were pretty much made for each other.
Mileage will vary, and maybe it’s because I just watched every single Sanvers scene of the season last week
(for science/research reasons, okay?) , but I think the progression felt realistic. If Maggie and Alex were younger, say, 23 or under, I might be more inclined to think Alex shouldn’t be proposing to her first girlfriend so soon, but they’re not; they’re around 30, and they both know their own minds and have strong personalities. Not to mention, they’ve already declared they want a lifetime of firsts together, which is a kind of proposal in itself.
Alex knows how fragile life can be, knows she and Maggie both work extremely dangerous jobs; add on top of that Kara’s plea for Alex to 'Never let her go’, and how close the entire city came to being destroyed, and I just think the moment played out right. It doesn’t mean I want to see a wedding in like episode 2 of season 3. Engagements can last a long time, and there’s plenty of material for them to mine from before an actual wedding (more Maggie Sawyer character development and back story, damn it), but the blurted out proposal felt right to me.