I thought it was a subtle tongue in cheek reference to the Walt Whitman poem (O Captain! My Captain!), at first, so that shows how completely wrong I read the line.
That may have been an influence on the line. Certainly it was in the spirit of that style of poetic apostrophe (O Somebody...)
When I read the scene I took it as overt flattery, somewhat obnoxiously so, and not flirtation. I just saw her as manipulative and using her friendship to get her way. I guess I'm just naive but her being flirtatious had not entered my mind.
No, you got it right on the nose, except it wasn't really obnoxious, since they were friends and it was done in a teasing manner. I guess I didn't convey the nuances as well as I could have.