This is even funnier in context.

Nene and Botan walked north past the roaming Towa.

Towa killed Okayu after itching to do so after a while. Then she headed north as well, thinking that there won't be anybody up there... immediately leading into this picture.

Why did Nene and Botan turn around?
Nene was afraid of Botan and suspected her to be an impostor. Fearing for her life, Nene ran back in case that she's being targeted by Botan.

Botan trusted Nene, however, and chose to stick together with her because of safety in numbers.

Towa was foiled because Nene was being Nene.