In Ashraf's letter, she asked after the Prime Minister's 1-year-old daughter, Neve.
Ardern wrote back saying that Neve was very well.
"She's growing up so quickly. It's amazing to hear her start to speak [she now says 'hi' to everyone she sees!]."
In her reply, Ardern thanked Ashraf for her words of encouragement and said her expression of solidarity had helped New Zealand.
"Knowing that we have friends around the world, who are prepared to stand with us to spread love and solidarity rather than hatred and division, has given us strength," Ardern is quoted as saying.
Although the news report does not explicitly say what this is in reference to, it's highly likely Ashraf's letter was about Ardern's response to the March 15 terror attacks in Christchurch.
Ardern also noted that she had heard of the beauty of the Kerala region of India, where Ashraf is from.
"I hope to see it for myself one day," Ardern is quoted as saying.
Ardern has not yet been to India during her tenure as Prime Minister.
But she has met with the country's Prime Minister, Narendra Modi – once at the UN General Assembly in New York in September, and once at East Asia Summit held in Manila in November 2017.
In May, she congratulated Modi on his re-election as Prime Minister.
"New Zealand and India have a close and long-standing relationship based on our shared democratic values and Commonwealth heritage, and growing trade, tourism and education links.
"Our relationship is underpinned by New Zealand's Indian community who engage across New Zealand's business, government and civil society."
Ardern said she looked forward to continuing to strengthen the two countries' relationships in the coming years.
