One of the more enjoyable things about “The Husbands of River Song” is the way the Doctor gets to see River being herself, unawares of who he is. This predictably leads to much consternation and disappointment for the Doctor, but in the end he sees she is the woman he thought she was, just maybe not exactly the way he would want that to play out.
The kind of love River has for the Doctor (and his reciprocal feelings) are a good standard for any married couple in a sense. Each loves the other with no demands. In fact, they operate under the assumption that their feelings are not really returned. River’s quote says it all:
“When you love the Doctor, it's like loving the stars themselves. You don't expect a sunset to admire you back. And if I happen to find myself in danger, let me tell you, the Doctor is not stupid enough, or sentimental enough, and he is certainly not in love enough to find himself standing in it with me!”
Of course the Doctor does, in fact, love her too, and he is, in fact, standing in it with her. He probably orchestrated events that led to him being there to save her.
Too many “lovers” today only give in expectation of return. True love is sacrifice, giving of oneself unselfishly for the good of the other.