Actually, the marriage you refer to is a bit trickier than that. As I recall, way back in the 1970s Denny O'Neil wrote a story in which Batman was somehow rendered unconscious (I forget how) and then woke up aboard a ship belonging to Ra's al Ghul. Ra's basically said something like, "Congratulations, Detective! You are now married to my daughter!"
Batman says pointedly, "I don't remember saying 'I do!'" Ra's regards that as an unimportant detail, explaining that in the native culture of Talia's mother (I think), all that is necessary is for the girl to voluntarily say "I hereby marry you" or words to that effect. Which Talia did while Bruce was still unconscious.
So Ra's feeds them a sumptuous dinner to celebrate the wedding and then locks them up in a stateroom aboard the ship so they can have a wedding night together. Batman knocks Talia unconscious, picks the lock on the door, and escapes back to the mainland to do something-or-other to foil Ra's al Ghul's latest scheme.
That story is reprinted in the TPB "Tales of the Demon," along with a bunch of other stories Denny wrote at different times in the 1970s about Batman, Talia, and Ra's.
All of the above "really happened" in the continuity of the 1970s.
So Talia is referring to that old story when, in "Son of the Demon," she reminds Batman of a time when she consented to their marriage. He says something like "I remember. But it's hard for me to think of that 'marriage' as real." Then she throws herself at him and they basically end up consummating their marriage -- probably some years after they "got married" in the first place (according to her mother's native culture's laws, whatever that culture may be).
For months after that (still in the pages of "Son of the Demon") they live together, apparently with Batman thinking of himself as being "married" to her, more or less. By the very end of that graphic novel they've broken up. But the "marriage" had technically happened, at least from Talia's point of view, years earlier in that old Denny O'Neil story, and as far as I know, that part is still in continuity and always has been! (Just not the part about Batman and Talia later having sex to "consummate" the marriage in "Son of the Demon.")
And now I hear reports that Grant Morrison has explicitly said he intends to drag "Son of the Demon" back into continuity, so that we can find out what happened to the child of Talia and Batman. (At the end of that story, she had told him she miscarried, but actually she put the kid up for adoption. The baby boy hasn't been heard from since, partially because Denny O'Neil later insisted "Son of the Demon" was way outside of continuity.)
Was all that clear as mud?