There is no offense:

if she travels with a group; if she travels where it is safe and free from danger; if there is an emergency; if she is insane; if she is the first offender. The eighth training rule is finished.

Theravāda Collection on Monastic Law The Nuns’ Analysis The chapter on offenses entailing confession The subchapter on lying down Wandering during the rainy season

Origin story At one time when the Buddha was staying at Rājagaha in the Bamboo Grove, the squirrel sanctuary, the nuns went wandering during the rainy season. People complained and criticized them, “How can the nuns go wandering during the rainy season? They are trampling down the green grass, harming one-sensed life, and destroying many small beings.” The nuns heard the complaints of those people, and the nuns of few desires complained and criticized them, “How can nuns go wandering during the rainy season?” … “Is it true, monks, that nuns do this?” “It’s true, sir.” The Buddha rebuked them … “How can nuns do this? This will affect people’s confidence …” … “And, monks, the nuns should recite this training rule like this:

Final ruling ‘If a nun goes wandering during the rainy season, she commits an offense entailing confession.’”

Definitions A: whoever … Nun: … The nun who has been given the full ordination in unanimity by both Sanghas through a legal procedure consisting of one motion and three announcements that is irreversible and fit to stand—this sort of nun is meant in this case. During the rainy season: not having stayed put for the first three or the last three months of the rainy season.