@SquigglesJP I know I'm 4 months late but..
On page 22 I think the sister means "purrs" not "rolls". From what I could find the sfx used seems to be "ごろごろ" which if the site I used is right (see note 1 below) can mean both "purr" and "roll". In the context of the scene and the character I think "purr" is the English translation that makes the most sense. Granted maybe in Japanese they say that cats roll, but I've never heard it used in English before.figured I'd give my 2 cents. =)
Also fun fact, most big cats can't actually purr. They "chuff" instead which sounds very different. So if she is a leopard girl she technically shoulder purr either. XD
Note 1 - I used the following site to look up the SFX: http://japan-and-me.com/japanese-sfx/