...and the kiss occurs after Willow comes and Satsu might have gotten into the room and has lent the lip gloss to some else.

It's hard to imagine Satsu leaving the battlefield in the middle of the fight. And lending the lipgloss to another slayerette just doesn't make sense as a plot twist - the reader isn't invested in any of the slayerettes, they're all just extras.

I can't believe Joss is playing with us like that.

Hee! Joss is evil! :))))