Scratching --> Tickling
If we go waayy back to
Chapter 55, we see Ji Bai reacting traumatically to a memory of Lilias tormenting. And now we have to wonder, was that "tormenting" actually a non-stop tickling attack. (And tickling can be bad, but yeah not as bad as what I was imagining from Ji Bai's appearance in chapter 55.)
"Chestnut" (aka Lilith) is Bai Ji's aunt (Lilias sister), the gamer principal of the school.
Bai Ji calling her "Mom" in her sleep instead of "Lilias". Tsundere towards Lilias. (Though obviously she has very good reason for having mixed feelings towards Lilias.)