She undergoes a series of tightenings, until she passes out, and then the garrotte is quickly loosened so she can revive, and then strangle a little again the next time.
Each time she revives, it takes her a while for the blackness to clear from her brain. Each time she wonders where she is until she realizes and remembers her situation. Each time, the horror is fresh.
And there is something new. She does not remember it, but she must have been struggling violently just before passing out. Because when she comes to, she feels the sensation of her pussy having rubbed itself a bit raw against the beam she straddles. She wonders whether she can offer sex in return for escape, even though she has gotten rather sore down there.