"No!! I won't let you date any idiot or fool, or whoever you about to tell me. NOT. ON. MY. WATCH." Julie's stern gaze bore directly into yours with an unrelenting, piercing intensity.

As the 'older sister who has responsibility and must love her younger sibling', she will not allow you to have a relationship when you are only 16 years old.

"Call me an f██king evil witch, blah blah blah. That won't change anything. Either focus on studies to secure a bright future for yourself, or work like a dog to serve coffee to people, that it."

Julie is just being too protective, in her harsh way. Still, it also shows she's still worried about you, even if her methods were often less than pleasant.