Bix Caleen's (Adria Arjona) story in Andor is one of incredible strength, resilience, and sacrifice.
At the end of Season 2, episode 9, "Welcome to the Rebellion," she leaves Cassian alone at the Yavin IV base. After waking up to find Bix gone—either having a nightmare or staring out of the window—Cassian opens his eyes to see she is well and truly gone.
But Bix knew if the choice was between the Rebellion and a life with her, he would go with the latter, and possibly neither of them would've managed to feel too great about the decision.
So, she takes it upon herself to choose him. However, we cannot grasp the magnitude of what she gives up when she walks away from Cassian, with whom she has built a life for the last couple of years.
At the end of Season 2, episode 12, "Jedha, Kyber, Erso," we finally get to know where she is. The finale takes us back to Mina-Rau before rolling credits, the planet they took refuge in after fleeing Ferrix. We get to see that B2EMO is safe and sound, thankfully. Then we see Bix in a crop field, with a baby in her arms, who is most certainly Cassian's child.
It makes Bix's sacrifice all the more poignant. She possibly knew she was pregnant and that a baby would have deterred Cassian even more from the cause. Her choice ultimately paved the way for Cassian to help create a better galaxy for a kid he didn't know he had.
That is why, despite being heartbreaking, the ending is one of hope—that thing they keep talking about in the Rebellion. Showrunner Tony Gilroy shared with ScreenRant that he had always planned this from the beginning.
"I had a good idea how much mileage we were going to put on these characters and how hard the road was going to be," Gilroy explained. "There's a shadow over the show, and I just knew, not dramatically but personally, there had to be a legitimate hope at the end of this thing, or it was really... not abusive, but just wrong."
"There has to be a candle in the window, or what's the point of getting up in the morning?"
Gilroy emphasized that he wanted the viewers to know, without a doubt, how much Bix was sacrificing. He even wanted us to be shocked by it because giving up the one good thing that may have happened to her after years of torture, anxiety, and sleepless nights takes an insurmountable amount of grit. It's a good thing Bix has it all.
"I really wanted to underline it for anybody who was doubtful about it. When they get to the end, they go, ‘Oh my God, she was pregnant. That’s why she’s leaving. Really? That’s what she’s not saying? Oh my God.’"
It is difficult enough to make people care about characters they know are doomed. It is even more difficult to end their stories on a hopeful note. Gilroy relies on you, the audience, knowing the future while the characters remain unaware of it, to weave a magnum opus of the most cosmic scale.