Various Puraans mention that thirteen of Daksha Prajapati's daughters were married to Dharma but none of those is Ahimsa. For example, Vishnu Puran Chapter 8 mentions the following wives of Dharma:
The patriarch Daksha had by Prasúti twenty-four daughters: hear from me their names: Sraddhá (faith), Lakshmí (prosperity), Dhriti (steadiness), Tusht́i (resignation), Pusht́i (thriving), Medhá (intelligence), Kríyá (action, devotion), Buddhi (intellect), Lajjá (modesty), Vapu (body), Sánti (expiation), Siddhi (perfection), Kírtti (fame): these thirteen daughters of Daksha, Dharma (righteousness) took to wife.
These seem to be the names of qualities associated with righteousness rather than the names of actual people still out of the given names perhaps Shanti could come close to Ahimsa. Further verses also mention their offspring strengthening our opinion about the abstract nature of these names:
The progeny of Dharma by the daughters of Daksha were as follows: by Sraddhá he had Káma (desire); by Lakshmí, Darpa (pride); by Dhriti, Niyama (precept); by Tusht́i, Santosha (content); by Pusht́i, Lobha (cupidity); by Medhá, Sruta (sacred tradition); by Kriyá, Dańd́a, Naya, and Vinaya (correction, polity, and prudence); by Buddhi, Bodha (understanding); by Lajjá, Vinaya (good behaviour); by Vapu, Vyavasaya (perseverance). Sánti gave birth to Kshema (prosperity); Siddhi to Sukha (enjoyment); and Kírtti to Yasas (reputation). These were the sons of Dharma; one of whom, Káma, had Harsha (joy) by his wife Nandi (delight).
Interestingly, the spouse of Adharma is also mentioned in this verse as Himsa both of which are opposites of Dharma and Ahimsa respectively:
The wife of Adharma (vice) was Hinsá (violence), on whom he begot a son Anrita (falsehood), and a daughter Nikriti (immorality): they intermarried, and had two sons, Bhaya (fear) and Naraka (hell); and twins to them, two daughters, Máyá (deceit) and Vedaná (torture), who became their wives. The son of Bhaya and Máyá was the destroyer of living creatures, or Mrityu (death); and Dukha (pain) was the offspring of Naraka and Vedaná. The children of Mrityu were Vyádhi (disease), Jará (decay), Soka (sorrow), Trishńa (greediness), and Krodha (wrath). These are all called the inflictors of misery, and are characterised as the progeny of Vice (Adharma).
As regard the mention of her being Vishnu's mother, that is explained by a similar list of Dharma's progeny mentioned in the Bhagvat Puraan. Following the order observed in the list of Dharma's wives, their children are, Rita (truth), Prasáda (favour), Abhaya (fearlessness), Sukha, Muda (pleasure), Smaya (wonder), Yoga (devotion), Darpa, Artha (meaning), Smriti (memory), Kshema, Prasraya (affection), and the two saints Nara and Náráyańa, the sons of Dharma by Múrtti.
Both Nar and Narayan are mentioned as Lord Vishnu's incarnations in the Puraans which is also confirmed in the Mahabharat:
In days of yore, O Partha, I was, for some reason, born as the son of Dharma, O chief of Kuru's race, and in consequence of such birth of mine I was celebrated under the name of Dharmaja. I took birth in two forms, viz., as Nara and Narayana.
Hence the sentence you have quoted in your question may actually be referring to this relationship and consequently it may help us identify the Goddess Ahimsa with Murti the mother of Vishnu.