She's their only daughter.

她是他们的独生女。

《牛津词典》

The young lady was Mercy Chant, the only daughter of his father's neighbor and friend.

那个年轻的姑娘是梅茜·羌特，是他父亲的邻居和朋友的独生女儿。

youdao

She's my only daughter.

我只有这么一个女儿。

youdao

The young man feels regret, which only grows as he falls in love with her daughter.

VOA: special.2009.05.04

But shop owners say now they only see "essential customers" those who have to buy for the marriage of a son or a daughter.

VOA: standard.2009.09.19

The couple's only daughter, Tamala is also a country singer under the name Georgette Jones.

BBC: George Jones, American country singer, dies aged 81

Kennedy's only daughter, Caroline Kennedy's personal experiences hardly resonate with the average woman.

CNN: How Caroline Kennedy could make a difference in Japan

' And (she) said to Oscar, 'Hey listen, that's my precious, and my only daughter ... she's my angel.

CNN: STORY HIGHLIGHTS