Dowan breathes, "And she was my only..."
I'm sorry but this is not a natural thing to say in that situation no matter how you look at it.
Your only what? Sibling?
Why would you say that? Obviously you don't have multiple siblings. But if you grew up with only one sibling, you'd never experience how it would be to have multiple siblings, so why put emphasis on "only"? And what's with the "and"?
And why don't you just finish that sentence in the first place? I tell you why. Due to the emotional shock, you were about to spill the beans but realized you were about to say something you were conditioned not to say because it is a taboo in your society and catched yourself just in time and put on the Mr. Spock mode.
"Love" would just make indefinitely more sense.
I don't let "friend" count either because it would struck me as odd that somebody who puts so much emphasis on family relationship would refer to his sister only as a "friend". Twin sister even, even closer bond! Blood is thicker than water.
Also, it strikes me as exactly the botched attempt at humour that is just creepy and awkward that I came to expect from crawl.