I hope it doesn't happen too but it is quite likely that Shien was captured, used as some noble family's personal panacea and poison creator... and probably also s*x slave since she is quite beautiful... I don't see how else she'd have survived when she apparently can only create potions and not use any other magic and apparently only wants to make people happy with her medicines and as such probably didn't have any weaponisable potions at hand during the witch hunts and since she was protecting Tama she had to delay the mob somehow...
I suppose one possible alternative is that she did die (or was in a near death state) but had some medicine hidden in her teeth or something and healed herself with it after the mob left. That'd traumatise her pretty badly too but since she said nothing happened at all I feel it's more likely she was locked up or trapped somewhere
Being tortured near death is likely since she can already heal a lost eye with a cigarette, and the mob wanted to get information on where the remaining witches are, so they might torture her, but being sexually assaulted doesn’t sound like what’s about to happen.
If legends about the succubus exists at that time, if they believe her to be a dangerous bewitching witch, no way they’d keep her alive for longer than necessary. Only extremely desperate, extremely rational or extremely ambitious people would actually try and use her.
And all I see from the mob is anger and fear. I believe if Shien got captured and refused to tell, they wouldn’t treat her any differently than any other witch, which is to her her burnt at the stake.
Which reminds me, it’s also entirely possible that she was already captured and burnt alive at the stake, but with witch medicine at the ready, she could prepare and revive herself when nobody was watching…which is certainly a very terrible scenario, but it’s the most likely one I can imagine, like what you mentioned.
After which she could hide her identity and pass off as a merchant, devote herself to a noble as a healer, or just hide and live off in the wild with the animals…at this point anything is possible.
But ultimately I would wonder how she’d keep her hat and not lost it after all these years and not reveal herself to the witch hunters. Especially when Tama explicitly mentioned that she had lost hers, so I would guess that the witches’ wardrobe may be discussed about in more detail in the future.