Once upon a time, somepony wanted a trainer who would brush her and treat her like a princess - so, she didn't struggle to be caught somewhere around Melona. She's a high-maintenance Pokemon so she demands a lot of attention and love. If she doesn't get it, she'll throw a tantrum and literally stomp her hooves around until Sooyoung gives her the affection that she deserves.

Also, yes, the Porygon suddenly appears to headbutt her. It will continue to do that every now and then because it wants to fondly remember how they met :)

Congratulations on obtaining a Ponyta ♂ lv20 and a Porygon lv22!