What I was going for in the first panel was Chelsea having zipped behind the tree so Speedy-Gonzales-swiftly that Millie hasn’t yet had the time to register her sister’s seemingly superhumanly sudden absquatulation from her field of vision.
That’s what I was going for… however, I’m not entirely convinced I managed to effectively convey this. Instead, Millie kind of looks like a little girl android waiting for someone to turn her on, flick her “on switch”, power her up.

So now I’ve picked that panel to bits, in the second panel, yes that’s a Chelsea-style Cheshire Cat homage.

From Chelsea in the rest of the panels on this page: a somewhat odd mixture of Etna (Disgaea) and Pippi Långstrump.
Gonzales to Cheshire to EtnaLongstocking. POW!