My niece said shes concerned; 15 years old, her height had been 52 (158cm) since shes 14. she grew a little during august 2021 and havent grow any taller since then. her mom is 161cm and father is 172cm. how likely can she still grow?

The limiting factor is the growth plates that support further increase in height. An x-ray of your wrist/hand could detect if your growth plates are open enough to gain that much height. If they are closed you are done. If you have grown 6+ cm in the past year you are likely to grow more. If you grew 3 cm or less in the past year you are almost finished.

Young women generally grow for 2-3 years after first menses, yet the hormones that make that happen start the clock that closes the growth centers. If she hasn't grown taller for about a year, she is likely finished. Expected final height based on both parents' height is 158.7 cm+/-.