I find an old note that 

Karve 1943-1944: 71 has remarked on the uses of mātṛ and ambā for both natural mother and step-mother in the Mahābhārata

Karve, Irawati. 1943-1944. “Kinship Terms and the Family Organization as Found in the Critical Edition of the Mahābhārata.” Bulletin of the Deccan College Research Institute 5: 61-148.. 

On Thu, May 23, 2013 at 1:01 PM, SOMDEV VASUDEVA <somadevah@mac.com> wrote:
It is probably worth noting that the Nāṭyaśāstra’s chapter 19.21–29, which lists stereotypically acceptable terms of address for women, does not include mātṛ. It does include ambā, but only to address an elderly lady (vṛddhā).

Somadeva Vasudeva

On May 23, 2013, at 6:04 AM, Howard Resnick <hr@IVS.EDU> wrote:

> Do we know the history of the Hindu custom of addressing women as  mAtA or mAtAji?

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