She knew all about him since before they first met.
And, if you want to make it even more confusing, he had met her before she was even born.
Some people say that they have complicated relationships. Melody Pond - also known as River Song, or sometimes Professor Song - would know that feeling better than anyone else.
The first time that she met him - well, wait, that's hard to explain. The first time that she met him in her own timeline, she still had her other body. The darker one, the one she'd grown up in, the one that Amy and Rory knew as Mels. Mels, Melody, the person who they named their child after. Melody Pond was her parents' childhood friend, and she was named after herself. Time is a funny thing, isn't it? Fun little situations like that take a good bit of getting used to. She's not really fazed by them anymore.
Anyway. Back on topic. The first time that she met him, her goal was to kill him. That's the best way to start a relationship, she thought. Passion and adrenaline. In the middle of Nazi Germany. In Adolf Hitler's office. She thought she knew the Doctor then, but she really, really didn't. He seemed so simple. So predictable. Classy, clever, fearless, stinking of ego. The stereotypical self-righteous vigilante. He probably deserved to be assassinated sooner or later, she figured.
But something deep inside of her twisted when he was beginning to lose his coordination. Something in the words transferred through the Teselecta from Amy. Something in the face and words of Rory. With those emotions seeping through her cold outer shell, she felt herself weakening. And with that, all of her assassin-training crumpled into a useless heap.
How could she possibly think of killing a man when he had such a beautiful sense of sympathy?
River was reliant on nobody but herself. She knew that, and she embraced it... but she couldn't bring herself to be entirely independent.
She cared too much about others. About him.
On one of many archaeology expeditions with her team, a young assistant had turned to her and asked a completely unexpected question.
Why did she always jump off of tall things backwards?
River had laughed. It wasn't something she realized that she did, she had told the assistant. Odd habit. Never really thought it through before.
The question lurked in the back of her head. Even when she first met the Doctor, that habit had already formed.
And then she realized.
River Song was considered to be strong. No one could outmatch her. She wasn't just a girl anymore, she was a woman. Skilled in countless styles of combat. Powerful. Knowledgeable. Creative. Witty. Able to get out of even the most impossible situations. Younger archeologists and friends had looked up to her, wanting to reach that level of self-confidence.
What they didn't know was that she understood the idea of death better than a lot of people. She herself had regenerated once, and had given the rest of her lives to her beloved timelord. She was trained as an assassin. She had killed in the past when necessary, and would kill again without hesitation.
There's something about falling that no other experience can capture. Weightlessness, helplessness, and the fear of the solid surface rushing up and up and up to meet you. Death is so unbelievably close. And she used to be afraid of heights, too, not that she'd tell that to anyone. She was fully convinced that one wrong twist would snap her neck against the cold unrelenting concrete.
River fell backward because it was her way of telling death, "fuck you, I am the master of my own destiny." She did it because it was her expression of how, despite the fear of death, she knew that she had power over what would happen. She was out of reach, and nothing, not even death itself, could grasp ahold of her. The whole of time and space was at her disposal. Wind buffeting her body, her eyes closed. It felt like flying.
The first meeting for him was the last meeting for her.
River definitely hadn't expected him to show up. The 51st-century planet-sized information collection was empty of life, but full of books- all of space and time recorded in their countless yellowing pages. The Library, that was her reason for being there. "4022 saved, no survivors". What kind of archaeologist wouldn't want to go see what was going on?
He wasn't the version of him that she was most familiar with. This version was taller, even more gangly and skinny. He was nicely dressed, and had hair that seemed to defy gravity. Attractive. The confusion on his face was amusing. It was difficult, though, to wrap her mind around the fact that he didn't know her. Didn't know his own wife. Didn't know the woman who'd been imprisoned for his very own murder. It was very difficult to refrain from telling him to much of his future.
What she did for him that night was something that she couldn't have done for anyone else.
She had no regrets about it. River Song believed that she controlled her own destiny, and if that included the way in which she would die, then so be it.
She remembered - as she closed her eyes, as the world grew blindingly white - about falling backward. The power and the confidence of it. She'd fallen, yes, but she'd fallen in love this buffeting her body, her eyes closed. Love was stronger than she'd ever expected. And she knew that this time, even though death was rushing up to meet her...that this is what she had chosen. What a way to die, she thought. For a noble cause.
There's something about falling that no other experience can capture.