Natasha tells Daniel that it's hard to love someone when they don't love you back. She knows that he wants to tell her that Samuel certainly loves her and that all parents love their children, but Natasha knows that it just isn't true. She knows for sure that Patricia loves her, but she heard her father say that she is his greatest regret.
Natasha fails to realize that the presence of regret doesn't have to negate love; the two aren't mutually exclusive. In addition, her father could have been speaking out of frustration or anger and possibly didn’t mean what he said. This shows that Natasha is experiencing more of an emotional reaction to her father's words than she'd like to admit.