"I'm not someone who can be controlled" asserts the speaker's independence and autonomy. It implies a strong sense of self and a resistance to being manipulated or directed.
"I want someone who will watch me do my thing" suggests a preference for a partner who respects and supports their individual pursuits, interests, and ambitions.
"And be like, 'That's my girl'" conveys the idea that the ideal partner would take pride in the speaker's accomplishments and endeavors, offering encouragement and affirmation. In essence, this quote expresses a desire for a relationship characterized by mutual respect, where both partners are free to pursue their passions and interests independently, while also celebrating and supporting each other's achievements and endeavors.