I think, aside from the show going for max angst, she just got SUPER freaked about her dad and it was her first instinct, paranoia that even being seen with Sterling would confirm everything anybody was suspecting. Maybe her first reaction had even been to go to her and that would have scared her even more, especially when it seemed like her friends (”friends”) were kind of suspecting something too. She does tend to react first and then settle down, like with Luke, as she then did with Sterling, but it’s hard to shut down that first instinct.