I posted this one but think I actually deleted it so if it is a duplicate I apologize. Best advice I can give you is to be there and reassure her that you are not leaving. Say it as often she needs to hear and for as long as she needs to. My husband and I have been together for 23 years and married 20 this fall. The only people that know about it (besides my providers) are my husband and best friend. My husband still reassures me frequently that he isn't going anywhere. I have talked to my best friend about my fears of hubby leaving and she tells me that she has talked to him when I wasn't there and she knows for a fact that he is there forever.

Also remember this is a very emotional time for her with all the hormones out of wack. Plus a lot of women get scared and old wounds may be opened. So if she think you might leave her, that only adds to the fear.