She's being held captive by Negan (Jeffrey Dean Morgan), and it doesn't look like there's any way out alive. Her friends aren't coming to break her out. Eugene (Josh McDermitt) isn't going to help her escape — but he did give her some poison pills after she asked for his help in killing herself.
Plus, Sonequa Martin-Green is a lead on the upcoming series Star Trek: Discovery, so she needs to keep her schedule clear to focus on that.
Sasha's arc this season has paralleled a comics character named Holly who also was taken captive by Negan. Negan offered to return Holly to Alexandria in exchange for a meeting with Rick. She had a hood over her head when Negan was turning her over. When the hood was removed, it was revealed that Negan had killed Holly and she had turned into a walker. She bit Denise before being put down by Rick.
Initially, we thought there was going to be a prisoner exchange scenario. Dwight (Austin Amelio) is currently being held in a jail cell in Alexandria while Rick (Andrew Lincoln) and the gang figure out if he's really willing to help them fight Negan. They could say they captured the high-ranking Savior while he was on a scouting mission or something and use him as a bargaining chip to get Sasha back, and then he could work as a spy, feeding information on the Saviors from the inside. In exchange, Negan would turn over Sasha, and then the Holly reveal would happen.
But then we remembered that Fear the Walking Dead did a prisoner exchange during which a hooded prisoner was revealed to be a walker in the Season 2 episode "Captive." Fear showrunner Dave Erickson said its resemblance to the Holly scene was a coincidence, but it seems unlikely that The Walking Dead would cannibalize its spin-off.
And then we read a Reddit thread in which users speculated that it would go like this: Negan fully intends to turn Sasha over alive, but Sasha has already taken a suicide pill. The Saviors don't know she's done this, and she didn't know she was going to be returned safely. She dies on the way, likely with a bag over her head. The Saviors then release her. When the hood gets taken off, she bites someone — most likely Eric (Jordan Woods-Robinson), Aaron's (Ross Marquand) boyfriend. Eric got some character development last week, which is a death sentence for a peripheral character. The Alexandrians think turning over Sasha dead was Negan's plan all along, and they start shooting. It's possible that Negan was planning to turn over Sasha in exchange for the guns he found out Alexandria had, though them having the guns at all is against the rules and it's unlikely Negan would be willing to negotiate about it.
That's a pretty convincing case for how it's going to go down, isn't it? We won't know for sure, though, until The Walking Dead's season finale on Sunday at 9/8c on AMC.