Whether or not a girl can grow taller at 18 depends on whether or not her epiphyses have closed. At 18 years old, the epiphyses have closed and can no longer grow taller, but if they have not closed, they may still grow taller.
There are a small number of girls whose epiphyses have not yet completely closed at the age of 18, and their development is relatively late, combined with a better diet with more protein, and foods containing more vitamins, there is generally a certain amount of room to grow taller. But there will be no significant growth and rapid growth.
Most girls at the age of 18 have basically closed their epiphyses completely, and with poor nutrition, there is no more room for growth of the long bones.
Whether a girl can still grow taller at 18 years old, it is recommended to go to the hospital to check whether the epiphysis has closed, under the guidance of the doctor for calcium supplementation.