I don't really get what's the relation of Liv being a "sex symbol" and her portrayal of Arwen in the movies. Are you disgusted by her because she's a sex symbol? Is that the first thing that comes to your mind whenever you see her whether as Arwen or just Liv herself? Does that change Arwen's or Liv's character? Why exactly are you saying sorry? I'll understand if you don't like Liv's looks or charisma or Arwen as a character, but saying that it's because of being a sex symbol is shallow and too condemnatory.
But while we're at it, Orlando Bloom is considered as sex symbol too by now, to think that most women are drooling and lusting over him. And so is Viggo Mortensen and the other actors in LOTR. Does it also change your view of them? Do you even think of Orlando or Viggo being sex symbols whenever you see Legolas and Aragorn in the movies?
Just to clarify this, you don't have to make sexy movies to be a sex symbol, so don't give me that argument if ever.