An Imploding Star

Isabella Johnson was a marine, until she was in close proximity to an exploding bomb which landed her in hospital, with no idea who she was anymore, she was forced to question everything.
From a young age, her best friend Sam had been the only person there for her. Her parents left her when she was born, both terrified by the idea of a child. Sam was the only person who got her through growing up in the orphanage, they spent every waking hour together.
Now, they're still best friends, though they've gone slightly different ways, he was in the Air Force and she had chosen the Navy, though now they're both out and trying to find their way around the world.
That is until Sam introduces her to his new friend, Steve...