It's technically true. Stevie heals fast, she's been reunited with her gem. Physically, she's completely 100% fine. Her whole life she was born and trained for battle. The violence, the stress, the parts of it that bother her, are difficult for her to acknowledge. They're her normal.
Of course she'd be okay.
"You know I'm sixteen, right?" Stevie smiles a little. She's used to ageless aliens not knowing quite how to address humans. She's practically a young adult!