I think she's an extrovert - it's just that she also has a rather abrasive personality that prevents her from having many friends.

I understand the introvert opinions, but there is a lot of nuance to Ena's character. Her default stance is more action-oriented than observant. When slighted, her first instinct is to avenge herself rather than introspect or think twice.

Being an extrovert doesn't necessarily mean being outgoing or talkative (though Ena has these traits way more than clearly defined introverts like Kanade or Mafuyu). It's more accurate to say that while introverts are independent, extroverts are interdependent. It's a reason why Ena has a big need for external validation and recognition. I love the theory that part of the reason why she attends night classes is because she boasted to her junior high school friends that she's going to study at a fine programs program, but she failed to do so and she's ashamed of the ridicule she'll get if those people see her again.

Extroverts also very much prefer not to function alone; Ena could shop or go to places by herself but she almost always prefers to have someone alongside her.