This will be short and simple reasoning to why she is alive. I will not go into detales. moiraine said to Thom in the shadow rising on page 279 "and I will see you again" just after she has given her promise to give thom the names of the aes sedi that stilled his nephew, now thom does not see her after that, but you must remember that Moiraine had gone threw the doorway that was in the Great holding in the Stone of Tear.and when you read the passage you will see that moiraine put special empishis on "will". that leads me to think that she knows without a doubt that she will see Thom again from her experience in the doorway. oh, I think that thom will be the one to rescue her, but i have no proof, so its not a real theory.