I'm sure her inclusion and removal was thrashed out back in the day, somewhere. I'm not going hunting for it.
In the wake of TH's last EE I think we can safely expect the release of a 6 film box set, probably with new extras and maybe more deleted scenes. Do we think Arwen's appearance at Helm's Deep should be reinstated, or at least given a place in the extras somewhere?
Tauriel was generally well accepted and Arwen could certainly continue the lady-like orc slaying. I'd be interested in seeing how she was originally going to be included.