Gilad,
I'm not an expert, it's just that your voice seemed somewhat "receded" in the mix. Hers sounded more intimate, as if she were closer to the mic and yours had been recorded further away. It's very subtle, but in a small way, it made you sound as if you were backing her up and not an equal duet partner (as I felt you should be). I hope it doesn't seem like nitpicking, sometimes I focus on weird things. It sounded great!