Despite her stellar career as a model, singer and actress, Taiwan singer Vivian Hsu is probably most proud of her role as a mother.

On Wednesday (March 3), Hsu posted a heartwarming picture of her with her family. They had thrown an early birthday surprise for the singer, who will be turning 45 on March 19. The celebrity was all smiles and followed up her post with another picture of a letter written by her two step-daughters Clara and Elisha, who could not attend the party.

"I'll always be here to support you, whether it's at home or when you're out working," Clara wrote. Shasha ended her letter thanking Hsu for being "such an amazing mother".

Since her marriage to Singapore-based Indonesian businessman Sean Lee in 2014, the star has settled down in Singapore and become a stepmother to his two daughters Clara, 16, and Elisha, 19. Hsu also gave birth to son Dalton Lee a year after the marriage.

Following a difficult pregancy, the singer has been experiencing a series of health complications, from bad colds to wild mood fluctuations. In her most recent Instagram post of her stepdaughter's letters, she also revealed that she had been diagnosed with gastroesophageal reflux disease (GERD), a digestive disorder where acidic stomach fluids rise back into the esophagus.

Hsu said her poor health was a result of her busy lifestyle and that she had recently begun adopting healthier habits such as sleeping early and eating healthily.

Her efforts have not gone unnoticed by her family. In their letter, both Clara and Shasha thanked the singer for taking care of them the past few years and showered her with words of support and admiration.

In her captions, Hsu expressed her gratitude to the girls, writing: "I'm so grateful to have been blessed with two sweet daughters. Although I'm not perfect, thank you for your understanding and love. I love you too."