This is interesting that you brought this up because there’s a very revealing video interview with Lana Parrilla that someone linked to today at IMDb. http://www.spoilertv.com/2012/06/once-upon-time-2012-bell-media-upfronts.html
(I’m going to focus more on everyone else’s true love in another post because what I had written did seem way off topic from Regina.) Anyway, I guess this does in fact confirm that Daniel was her one true love. I figured that he was because it was suppose to justify Regina wanting revenge on young Snow forever. Although I felt really bad for Lana Parrilla because Daniel seemed like the only single male character that she had no chemistry with whatsoever.
So unfortunately, I do think that their scenes can come across as Regina being more about rebelling against her mother and only liking Daniel because of that or because he’s the only one that she’s able to confide in about her mother instead of the passion and chemistry that we saw with other true love couplings that have been confirmed on the show like Snow and Charming or Rumple and Belle. I don’t want to blame either actor because I think they did fine, it’s just they just didn’t seem to have any kind of chemistry at all. Plus, chemistry is totally subjective too as evidenced by how many ships are out there.