The Stranger Things star, who has been in Bali for the last 10 days, thanked staff at the Mulia Bali beach resort for being so attentive.
In the sweet message shared on both Twitter and Instagram, she began: “I would really love to thank all of the staff at the @themuliabali for taking such good care of us while having to extend our stay here.
“I cannot thank you enough! Also, to the Balinese people who are the sweetest, kindest and most humble people I've ever met,” she continued.
Commenting on the current situation in Bali, she added: “But most of all, my thoughts and prayers are with the people whose lives have been affected by this. I truly hope everyone there stays safe. Sending all my love to Bali… Until next time.”
The 13-year-old actress’ post has garnered more than 3 million likes on Twitter and nearly 2 million on Instagram, respectively.
Fans of Millie, who plays Eleven in the Netflix series Stranger Things, were quick to praise her.
One wrote on Twitter: “This is so kind and thoughtful Millie. You look so peaceful and happy in these photographs. We love you!,” while another added: “Palms for this wonderful person with a huge heart.”
A third posted: “I cannot believe, you’re perfect, you always think about others, you’re kind to everyone, you have a big heart and that’s what I admire most about you, never change that.”
Millie also shared several pictures of her stay alongside the lengthy message. In one particularly idyllic snap she appears to meditate on a cloth with ornaments beside her.
In another photograph, the Emmy nominated actress strolls along a pathway with the beautiful backdrop of Bali in the distance.
The actress had only travelled to Bali for a four-day break following her work commitments, but it was extended after news of a volcanic activity was reported.
Millie, who has won several award this year, will be starring in Godzilla: King of Monsters, which will be released in 2019.