Cambodia is primarily Buddhist. Next door, Thailand has a Muslim minority in the far south. Myanmar (formerly Burma) has the Rohingya minority group who predominately followers of Islam:
https://en.wikipedia.org/wiki/Rohingya_people
The names of the family in this attack appear to be Pakistani. Acid attacks for various reasons are a common feature of disputes in Pakistan and India (and to a lesser extent in other Muslim countries in South Asia). They are one of the lovely cultural enrichments that came to the West with recent waves of immigration from these parts of the world.
My guess is she rebuffed someone, maybe a potential suitor, and they (or their family) made arrangements to get revenge. It is a cultural, not necessarily a religious, act. Sort of hurting a person in a way they cannot recover from. The attack could possibly been carried out by a third party that has now left the country on “vacation.”
Sorry, you are just plain wrong. Acid-throwing started in the west. Specifically it started in the U.K., because that is where industrialization started. When industrialization started in the U.K. in the 18th century, people started to have access to substance like strong sulfuric acid (aka "vitriol." And that's when acid throwing started. It reached it's peak in the second half of the 19th century.
The countries you talked about had industrialization much later.
See posts #27 - 31.