Nityaa is a feminine form of Nitya (Eternal).Devi Adya-Shakti is eternal.
The mantra 64 of Chapter 1 of Sri Sri Chandi reads
Nityaa eva saa jagan-murtis tayaa sarvam idam tatam, meaning Goddess is Nityaa, the entire world is Her body and She is All-pervading.
This is the most beautiful depiction of Nityaa.
So ALL the forms of Mother Goddess that we worship are Nitya.
Yes, Dasa-Mahavidyaas are also Nityaa-s.
In specific purana, some particular form of Devi has been also named as Nityaa along with Vajra-prastarini.I do not have the reference with me at this moment.Hope someone wil be providing the details of that form.
But I repeat, All forms are Nityaa and Sri Sri Chandi is the most respected scripture among all the scriptures depicting the Mother Goddess.
Nityaa alongwith Lalita and Vajra-prastarini, Annapurna etc are the devies of the Purva-Aamnaaya, according to Devyaagama-vachana in Tantra-Rahasya. Lalita is one name of Srividya. So according to this scripture, these two are related. (Reference: Sastramulak Bharatiya Saktisadhana, Upendrakumar Das,RMIC, vol 2, page 1049).But Sri Vidya explicitly is treated in the Samayachaara-Tantra as belonging to Purva-Aamnaya, and there Nitya is not mentioned.