I don't want to say who is right or wrong here.
I would just say Sri Lankans have their own way of dealing with things. We call random strangers on the road uncle and aunty or Ayya and Akka.
When working in Sri Lanka, It depends on the context. For example, if someone from the top management joins a random call, you don't address them as Ayya or Akka. You would just say their names. (maybe in the gov institutes, you would call them Sir or Madam). But if there is someone who you work on a daily basis, side by side, even if they are senior or junior, I think it's the Sri Lankan way to address them in a more informal manner.
My best guess is, in this very case, she had a cultural clash given her background.
I believe she has the right to be comfortable in the form of address she use. It is invidual. What I don't agree is to label something as unprofessional just because it doesn't align well with how things are done in other cultures.
