I don't find Cassandra attractive and I think she does look masculine. I don't really care about the plethora of reasons someone can come up with that mark her as feminine and perfect in their eyes, because their eyes and opinion is not mine. Her features are gaunt, angular, predatory and uninteresting. Her hair looks like it was cut with a knife in the field and she wears her scars proudly, she also makes no bones about being a tomboy and basically acting and being just like her brother to carry on his legacy. So not only do they remark that yes she does act like a boy, they give you a reason why as well.
Now to some this may scream awesome female warrior but to me its a lame choice for the only straight female in the entire game that your straight male character can have a relationship with. I can pretend or role play to a degree but in truth most RPing is usually a shrouded extension of yourself so more often than not you come back to what you yourself are comfortable with. If I don't like a short haired tomboyish woman, then I don't. No measure of angst or insults is going to change my mind, nor is someone telling me my tastes are simple going to bother me. I've tasted many fruits, been to many countries and have found my preferences.
To that end, if you love her look then more power to you, but I find it disheartening that people ask for leniency and liberal philosophy when they condemn what someone else likes with little more reproach than "You have no taste". It's all subjective and there is no right answer, people like what they like. Let them like it and mod if they want.