Sometimes I open her inventory to take things from her.
Sometimes I open her inventory to give her something like a weapon, or armor, that she can (and sometimes does) use.
I'm not always trying to give you that heavy warhammer that I want to sell but don't feel like carrying! She should have a couple more options for speaking in the situation where I ask to trade with her. Perhaps she only says this if I give her something heavy that she doesn't plan on using, like a warhammer or something. If that's too complex, just give her a few other random comments to say. Also, throw in a few "silent" options as well! It wouldn't kill me if she just didn't say anything at all from time to time.