Guitar strings are precisely the same thing just on a different scale and, they're readily available. I think you'd be wise to think hard about using this as a choice of weapon because thin wire is difficult to hold (it could easily cut the murderer's hands) unless the killer fashions some sort of handle on each end of the ligature. Also, it takes a lot of strength to kill an adult using a ligature. Think about how hard you'd fight if someone cut off your air supply. Normally, this would not be a good choice of weapon for a female to use against a male.
I've seen a few deaths caused by garrotting and hanging. Neither of the killers used the same material - pantyhose, twine, leather strap, rope, shoestring, etc., and rarely was the skin even broken. Not even remotely close to a decapitation. One guy used baling wire which would be similar to your scenario. In that case the flesh was badly bruised, but I don't recall any bleeding at all.