Responses
Spoiler
I think they met already, mother was disguised as the grave keeper, and she directly knew Ruby was a girl.
Nope she doesn't know that the girl was ruby in the next 1-2 chapter in the hot spring she will discover that she is a girl when they accidentally meet
What if the 'mother' come across Rubi in them Onsen???bim so excited!!! I hope that's the case