This is not an obvious achievement. You have to fulfill 2 conditions:
1 - Taylor can not die before "Reflections" chapter. (Here I will give you a tip! in chapter "Pursued" when you reach the museum as Taylor and Daniel you will able to find a knife! It is in the room where Taylor has her vision and as Daniel you have to recuse her, then take the knife and give knife to Taylor!!!! Then in Chapter "Low point" when monsters attack you as Andrew go help Daniel first, when you recuse him you will able to recuse Taylor and use her knife to "untie" her and both will survive :)).
2 - In "Reflections" chapter after a Daniel and Andrew vision in the past, a monster will catch Taylor and as Daniel you will run after her, then choose "Follow Sounds" and then as a Taylor you have to choose "Get out of here", then you gonna need to finish QTE (QTE = It's this minigame when you press B,X,A and Y to survie) as a Taylor. After that Daniel and Taylor will come back to rest of the group and achievement should pop.
IT WILL ALSO! Unlock the another achievement - "Our Own Demons" so this is 2 in one :)
I am sorry if something was not wrote correctly but I am not native english speaker but I tried my best to describe it easy.
If you have a question you can add me GT - BajerKR and I will try help :)