That's the face of fear.
Fear of getting it wrong, fear of doing an unknown *something* that will destroy the intimacy, fear of coming across as a loser unworthy of being liked or loved. Fear of being vulnerable and being "rewarded" for that vulnerability by being hurt.
On the other hand... speaking OF the hand... Millie's hand is right where she can feel Loona's heartbeat. Probably about 160bpm right about now. Here's hoping she can read those signs, and read the room, at a higher level than before.
So far so good.