I've always thought that Tewi was responsible for Mokou finding Kaguya in the first place:
1. She knows what's going on inside the Bamboo Forest, and would have known about Mokou, much like how she knew about Eientei.
2. She made a deal with Eirin ensuring humans would not approach them, but Mokou somehow ended up finding the princess anyway.
3. Kaguya would have been hidden inside Eientei, so Mokou finding her would mean the pyro finding the mansion, which would also mean Tewi didn't keep to the agreement in Mokou's case.
4. Mokou's official profile indicates that her meeting with the princess was through
luck.
Added to the fact that Tewi is a probable
cause of disagreements between the two, maybe it really is a
conspiracy...
To reference Alice in Wonderland, I can imagine Mokou following a white rabbit, falling down a rabbit (trap) hole, finding a pile of rice cakes with a sign saying "Eat Me", meeting royalty tending to her plants while surrounded by servants, and---after causing a ruckus---having the aforementioned royalty wanting to go off with her head.