In Jain Dharma, a mahāsatī / sādhvī can certainly have deep knowledge, purity, and the ability to give pravachan. She may also guide many people through her conduct, study, and teachings.

But formal sangh leadership is usually not based only on knowledge. It is also based on:

• āgamic maryādā
• paramparā
• vows and discipline
• recognized monastic order rules
• tradition of the specific gacch / sampradāya

So the main point is:

1) Spiritual knowledge and leadership are not the same

A sādhvī may be very learned and realized, but still not hold the formal post of Acharya / leader of the sangh in many traditions.

2) Pravachan is possible

A mahāsatī may give pravachan, explain Jain principles, and inspire even monks and nuns, if it is within the accepted discipline of her tradition.

3) Why not always lead the sangh?

Because in many Jain traditions, the role of formal sangh-nayak / Acharya-like authority is traditionally assigned according to lineage, vows, and established monastic structure. This is a matter of maryādā, not a judgment of inner worth.

4) Can she teach monks?

If she has scriptural knowledge and the tradition allows it, she may instruct, clarify, and discuss dharma. But in practice, monastic etiquette often keeps seniority and order intact, so the form of teaching may differ from a public sermon.

5) Important Jain understanding

In Jain view, ātmik guṇ are what matter most:

• right knowledge
• right faith
• right conduct
• non-attachment
• austerity
• compassion

So a mahāsatī may be highly revered and spiritually powerful, even if she does not hold the formal position of sangh leadership.

In short: she can be a great teacher and spiritual guide, but formal leadership of the sangh is generally determined by monastic tradition and maryādā, not only by realization.