Wheatley said:
I never said I agreed with the genocide of the geth (I tried to convince Tali and the admirals to open negotiations) but she at least has some weird, twisted justification for it. Ashley just grumbles and bitches about how shes surrounded by inferior aliens, and is incredibly hostile to Liara for one. The n she shows up for about 5 minutes in ME 2 to ***** at you, where many people just wanted to finish the mission and go home to a good LI.
Her grandfather is the only human to surrender to aliens. As a result, she got shafted by the Alliance many times. Her holding a grudge against aliens is perfectly understandable, reasonable, and, well,
human.
She's hostile to Liara because if your a male, she see's someone who could try and take you away from her. In other words, jealousy, which is another human trait. If your female, well its because she just got on the ship and appears to be taking control of everything. Knowing her history, its obvious she would react this way.
Her views also change throughout the game. After talking with you plenty of times, she re-thinks her stance on aliens, and changes. She's more accepting of them after you talked with her. She changes because of the situations that she's been in.
And she bitches you out in ME2 because your working with a terrorist organization known for ruthlessly killing aliens(and preforming horrid tests on humans). How would you feel if someone close to you, who talked you into accepting another culture, and then came back 2 years later doing secret missions for some racist terrorist organization? An organization you actually fought against in the first game(the Cerberus quest chain in ME1 is the largest quest chain outside of the main quest). You'd be pissed off to, and demand an explanation. Of course you can't defend yourself because Bioware doesn't let you. But thats not an issue with her, thats an issue with the dialog system not letting you tell the truth.
Essentially, she's a fully developed character complete with a personality, beliefs, morals, thoughts, likes, dislikes, emotions, and all that good stuff that makes us human.
And for some reason everyone hates that, and prefers Tali for some reason. A girl who's infatuation with you is more annoying than cute.