What you wrote is correct, HOWEVER, it forms the wrong conclusions.
Right now she has no idea what the future is going to bring either. She is unable to plan that far in advance. Rick1963 is correct that she is protecting herself. As suddenly as she changed into this alien it is possible that she will emerge from the fog. She is playing out the script and although their are different variations of this movie, they all have basic themes.
You dont know that she will NEVER come back, but you should start living your life "as if" she might never come back. Subtle difference but I hope you understand.
I have said this many times before but the LBS gets to decide in the end. So if you feel you must completely shut the door to move forward then that is OK, but I suggest that you can always choose that. Leave the door cracked open with a small little wedge but keep moving forward.
Some day in the future(dont ask me how long) she will be back, that much I am sure.
