Growing in many ways with 成長

Kanji Explanation: Becoming and accomplishing with 成

Mina buys a can of coffee, even though she’s bad at bitter drinks. When her friends question her, she says she’s grown up a bit and should be able to drink it.

サナエ:: 「どのへんが大人(おとな)になったのよ。」; “What part of you has grown up?”
ミナ:: 「私(わたし)だっていろいろ成長(せいちょう)してるの！」; “I've grown in lots of ways!”; Literal: “Even I have grown in various ways!”

Key Points

1成長(せいちょう) is broad growth or development

成長(せいちょう) can refer to emotional, personal, or practical growth, not just getting physically bigger.
That broader meaning fits this teasing conversation about acting more grown-up.

2いろいろ成長(せいちょう)してる means I have grown in various ways

〜してる is the spoken form of 〜している, giving a present result-state meaning.
Mina is claiming that her development is already visible now.

3私(わたし)だって and の add a defensive insistence

私(わたし)だって means “even I” or “me too”, pushing back against being underestimated.
The sentence-final の adds emphasis, like she is insisting that her claim should be taken seriously.