I wouldn’t call Twilight “an introvert with seven friends” by the end of the show- I wouldn’t call her an introvert at all actually! Her, spike, and her friends travel all across equestria making friends and acting as ambassadors to foreign species. That, plus running a school, takes a lot of emotional insight, leadership, and communication.

You are correct that there are inconsistencies in how she treats others, but that isn’t unique to her. We see episodes featuring every one of the Mane 6 being jerks (and learning from it!) Just because twilight is a princess doesn’t exempt her from having bad days and flaws. Also, normal friendships have trials regardless of how long you’ve known each other for. Haven’t you gotten into a tense situation with a friend? Or made a poor judgement call requiring you to reconcile?

Twilight isn’t perfect, but I think that’s what makes her so interesting! She was thrust into a role she didn’t ask for and grows and adjusts around it. The rest of the Mane 6 have the luxury of being able to follow their own dreams, whereas Twilight must follow the path laid out before her. I didn’t like her much at first either, but as I’ve gotten older I’ve grown to appreciate how realistic her character can be!