In the "previously" clips for Star Trek: Discovery Season 2 Episode 13, there is apparently a princess who can turn herself invisible. She says "I ran away because I wasn't ready." in the clip. Tilly was featured prominently in the clip. What episode was that taken from?
If I am to believe this article she's probably an alien from the Short Trek short "Runaway":
The first Short Trek premiered in October of 2018 and followed a day in the life of Ensign Tilly. She has a frustrating conversation with her very overbearing mother that stokes her own self-doubt about joining the command program. Then, while eating alone in the mess hall, she discovers a young alien woman who’s used her ability to become invisible to stow away aboard the Star Trek: Discovery. After Tilly convinces Me Hani Ika Hali Ka Po she means her no harm, the young alien woman reveals she’s from a planet that’s about to achieve warp capability and is poised to join the greater space-faring community.
Found with the Google query
star trek discovery invisble princess.