your daughter seem to be having simply stretch marks
These are very common in growing age.
You should not be very bothered by them.
With time, they will become less prominent.
Initially these are red in color, later they fade and may persist as white lines.
Some people do suggest using retinoic acid
to decrease their appearance.
You can see a dermatologist
for the same.
Hope it helps,
Dr Geetika Paul.