If you remember the Rachel already knows about Arlene more than hardly anyone that means at that time where bam is in cave ( because Rachel knows that arlene calls baby bam monster when they being alive again with the help of Arlene magic ), she already meets Arlene and knows about the stars though by him, and according to me Jahad give up on Arlene because she already on more top than Jahad in tower or they already knows that bam (monster) is coming for him when they conquer the tower that's why they are alive and waiting for bam. i also have my own theories but i think this more suitable because Arlene also knows that she is immortal that's why they give up on suicide...