I agree with you, the slate should not be wiped clean. I like redemption stories, but in order to be redeemed, a person has to earn it. They have to turn from their evil ways and actually do good in the world.
Just to have a better grasp of this... Of what "evil" actions she's supposed to be guilty of so far in the game, exactly?
I have no idea, maybe we'll find out. I mean, maybe she hasn't done much. Maybe she just joined a profoundly evil organization innocently and has maintained her innocence despite being accepted into that organization. Maybe she's undercover. Based on all that I've read about the church of Shar though, I think she would have had to have done some evil stuff just to be allowed to be a cleric of Shar.
The thing is, though, just because someone does evil things, and can thus be coded as "evil", doesn't mean there can't be lots of good in them as well. People are actually a lot more complicated than just "I have an alignment, I am good or evil". A lot of people would be judged differently as good or evil depending on what time of the day it is, or what day of the week.
