A real problem with this one is that I don't know much about this song at all. It sounds like something that can be sung by someone like Christina Aguilera or Britney Spears.
OK, I think there is a part that the female says something that sounds like "together, happily forever". I can't really recall what was said, but if it isn't together or forever, then it could be words that rhyme while also containing 3 syllables. The 1st word is used at the end of a line (where together would be in this case), and after a short pause the person sings the next two words (where happily forever would be).
The singer sings in a gentle manner during the verses, which is also where those three words are. After the verse comes a part right before the refrain. The female still is singing in that same gentle manner, but it may be another female as well singing gently with her. Then shortly after is the refrain. The singer sounds more aggressive compared to earlier.
Now I still have a hunch that one of the two sang this song. I would say somewhere between the mid-late 90's to the early 00's is when this song came out, more than likely the earlier period. If I can figure out more I will try to post more.