She's definitely alive currently (I believe that may even have been confirmed by Martin at some point but I have no definitive reference). She's definitely currently leading Jaime into a trap under the orders of Stoneheart. I don't see either one of them dying at the end result of this altercation. I feel like this pending altercation will lead to a story arc and closure for Catelyn rather than Jaime or Brienne. When all is said and done I believe Jaime will die but it won't be there. I actually see Brienne making it to the end of the series in some capacity.