I'd like to know the answer to this as well.
Specifically, I ignored the first "flirt" option as I wasn't sure who to romance yet.
It would be interesting to know, though I always save right before attempting a romance just in case it fails so it's really a non-issue.
The "Flirt" options don't matter, only the "Romance" option at the very end.
And I dunno. On some characters I can decline romance and they'll never bring it up again, but on one of my characters MacCready occasionally repeats the "I hope I didn't bore you to death with my life story" line and I get the romance option each time.
When I romanced my companion I failed at a couple of flirts but I was still successful at the romance. Maybe it depends on the companion.
thanks for the answer, kinda thought it was like that.