One part of the picture that has bothered me, is why did she wait until they were walking away 20 minutes later to finally grab her phone and take a picture? If she was nervous about them, she would've taken the picture right away. I still think she took a picture of a random couple walking down the street. She was setting up her story.
It's amazing that with having that much time to concoct a story, "I fell asleep and when I woke up he was gone" was the best she could come up with. Followed now by, "I woke up and he was just dead in bed!" She's certainly not very creative.