Its always painful to let someone go who is the closest to us, not because of love but because of attachment. Love would instead make us think for the other's benefit, as you are thinking now. Attachment is selfish, love is not. And no one dies. We always carry people along in every birth. This bond of souls is not from this birth only. So don't worry !! You CANNOT loose her. May be you stay away from each other for a while, but you will separate, only to meet again :)