unexpected reaction?

So just recently one of my friends returned from her 6 month deployment. We weren't super close, but close enough that I knew she was done with guys for awhile during her deployment. I just hit 13 weeks pregnant, and when I saw her in person I decided to show her the ultrasound picture, knowing she would want to be in the loop and would be happy for my husband and I. 
I show her the picture and her face just drops. And she says "oh, I was once too." And then completely walks away. 
I wasn't looking for sympathy or a crazy reaction, but what the hell? Of course I would have been more careful with what I said had I actually known about her past.. but how was I to know? 
When I talked to my husband, he had drawn her blood before her deployment I guess (we both work in an ER) and her first hcg was positive and a week later it was not. I'm thinking a chemical pregnancy. But he never told me of course because of patient privacy. 
Thoughts? I still haven't approached her and she has not reached out to me.