Female Nunh?

[Allyrion]

Put short: There is zero evidence or even hints that suggest anything of the kind.

From what we know, Nunh is merely a title bestowed to the Tia who attained breeding rights, which can go either via beating the former Nunh or by convincing females to breed with him (founding of a new clan). Nunh status does not equate to leadership within a tribe, and in fact, very few nunh ever become leaders.

That said... it is very likely that female Seekers become leaders among their tribe. It is very unlikely that they'll grow a weiner and become able to successfully breed, which is all the Nunh status

I'm not sure that's true unless you have a different source.

From the lore book it says (under culture)

The Seekers of the Sun are a highly patriarchal culture, with each tribe centered around a strong breeding male (nunh) whose duty it is to form a harem and lead his people to glory and prosperity.

That seems very straight forward.

To the OP, I agree with others that there's no evidence of this happening to assume it is possible.
How alike they are to cats, biologically and behaviorally, is still up in the air.

However it does seem clear that Seekers societal structure was probably based around lions (especially since lions are the only really social cats). I don't think it's absurd to look at lion behavior and think maybe some aspect may be take place in Miqote tribes. I wouldn't be surprised if that's how the writers decide how to add such details in the first place.

But at least for now it's not known of and the Nunh being tied to breeding makes it unlikely. It's not totally far-fetched there might be an outlier tribe with a female leader though.