In Jainism, monks and nuns (sadhus and sadhvis) are expected to observe strict celibacy (brahmacharya) as a fundamental vow. Engaging in sexual activity is considered a grave lapse (aatichar) and a serious violation of the monastic code.

If a sadhvi violates the vow of celibacy, the prescribed prayaschitta (atonement or expiation) is severe. Traditional Jain texts, such as the "Vyavahara Bhasya" and "Nisitha Sutra," outline the following key points regarding prayaschitta for such a transgression:

1. Confession (Alochana): The first step is to confess the offense openly before the monastic community or to an acharya (senior monk).
2. Repentance (Pratikraman): The sadhvi must sincerely repent her action, acknowledging it as a grave fault.
3. Expiatory Penances (Prayaschitta): Depending on the seriousness and circumstances, the penance may include:

- Severe fasting (upavas or attham) - Special rituals of expiation (prayaschitta kriya) - Temporary or permanent exclusion from the monastic order (prayaschitta nishkasan) - Public declaration of the transgression and seeking forgiveness

1. Re-admittance (if allowed): In some cases, after fulfilling the prescribed penances and if the monastic community and acharya deem the repentance genuine, the sadhvi may be re-admitted into the order. In other cases, especially if the transgression is repeated or not genuinely repented, she may be permanently expelled.

The exact nature and duration of the penance depend on the tradition (Svetambara or Digambara), the rules of the specific sangha, and the acharya’s discretion.

References:

• "Nisitha Sutra" (Jain monastic disciplinary text)
• "Vyavahara Bhasya" (commentary on Jain monastic conduct)
• "Jain Monastic Discipline" by P.S. Jaini

Summary: A sadhvi who has had sex must undergo confession, repentance, and severe atonement, which may include fasting, rituals, and possible expulsion from the order, as guided by senior monks and Jain scriptures.