Saw Self Harm Scars On Step Daughters Friends Thigh

I (F35) went camping with my my step daughter and her friend, both 14F. While at the beach I'm 95% sure i saw self harm scars on step daughters friend upper thigh as she was pulling her shorts down coming out of the waves. My question is, should I let her mum and dad know what I saw? Or is it something I should keep to myself?