How can a 14 years girl grow taller after getting periods? what diet should she take?

No diet: Nothing will make her grow taller, genetics will mostly dictate how tall she will get.

About an inch or so: Puberty for girls overlap the start of menstruation (between 10-14 yrs) and they would generally add an inch and a half on average after their periods began. Diet or exercise have little effect on height development.

Hormones stop growth: Height is mostly determined by your genetics and general health and by age 14, the hormones of puberty that change your body and give you periods also close the growth plates on the bones, so that usually there is minimal height growth after 12 months. A healthy diet should include fruits and vegetables, dairy for calcium, meat or beans for protein and iron, starches for energy and some fats.