Mint is smug as can be (most of the time). She's very particular about her mannerisms and appearance. She portrays herself as very proud, elegant, and confident individual, but she's ultimately putting on a front to hide some deep-seated insecurities regarding how the family before her current foster family treated her. Underneath the front, she's relatively anxious, lonely, and afraid of judgement. This doesn't show often, but it breaks through every now and then.

If you're looking for a place to start with the voice: Cassandra Lee Morris is a nice example, particularly for playing Edea Lee in Bravely Default and Bravely Second, https://www.behindthevoiceactors.com/Cassandra-Lee-Morris/, and also Kara Eberle, who voices Weiss in RWBY.