I can't pick a stronger suit for her, so I would have to say both. Each fit her character based on which game you play. She's down to earth and somewhat timid (I guess) in X, so something along that dress was appropriate.

On the other hand, she gains a sense of adventure while travelling with Paine in X 2, so her newfound sense suits her well in the short skirt. She looks a little too provocative, yet she still has a sense of dignity about her.