In Jainism, this sentence can relate to two common topics:

1. “There is only one female Tirthankar”

According to Shwetambar tradition:

• Out of 24 Tirthankars, only one is female – Bhagwan Mallinath (19th Tirthankar).
• They believe Mallinath took birth as a woman and attained Kevaljnan in that same female body.

According to Digambar tradition:

• All 24 Tirthankars, including Mallinath, are considered male.
• Digambar belief: due to physical and practical reasons, a woman cannot attain Kevaljnan in a female body; she must first be reborn as a man and then attain liberation.

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2. “Only one female can be in a particular role”

Sometimes people say such a line while discussing:

• Ganadhar (main disciples of Tirthankars) – all are male.
• Chakravarti, Balabhadra, Vasudev etc. – these are all defined roles in Jain cosmology and are male by definition.

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If you were referring to Mallinath Bhagwan as the only female Tirthankar, then:

• This is accepted only in Shwetambar tradition.
• Not accepted in Digambar tradition, where Mallinath is male.

If you meant something slightly different (like women and moksha, or women as monks), please tell me the full sentence or context, and I can explain that specific point clearly according to Jain Siddhant.