Susanne Der Krykor's body was discovered earlier this month at her home in the village of Yaqubya, after she failed to turn up to a prayer meeting she regularly attended.
A coalition of jihadist groups including Noussra Front - the Syrian branch of Al Qaeda - took over Idlib in 2015 after defeating Syrian governmentforces.
They imposed Sharia law on all residents, which led to many of the village's Christians fleeing from the region.
According to an Orthodox priest who spoke to charity Christian Solidarity Worldwide (CSW), less than 200 Christians remain in the region, compared to approximately 10,000 before 2015.
CSW's Chief Executive Mervyn Thomas said: "We extend our heartfelt condolences to the family, friends and community of Susanne Der Krykor.
"This heinous crime is emblematic of the violations being perpetrated against innocent civilians by the extremist groups that have overrun parts of Syria.
"We call on Russia, Turkey and the rest of the international community to find a sustainable political solution to the Syrian conflict, ensuring that vulnerable communities are provided the protection they so desperately need."
Susanne Der Krykor was a retired teacher of Armenian heritage in her early 60s, who volunteered most of her time to teach children the Arabic language and other subjects.
She regularly attended a weekly women's meeting at the village's church.
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