[Jonty]

I am 13 and live with my parents and am an only child, we have a great life with swimming pool etc, and I realise how lucky I am. This summer as my parents both work, instead of sending me to a summer placement, they invited my cousin to stay with us. She is 16 and her parents are divorced so they dont get holidays etc.
It was all ok but yesterday she said why dont we skinny dip in the pool, I was kinda shocked, as im quite shy of my body, but she said if she did it I had to. I eventually agreed, and tbh after a few minutes it felt fine.
When we went back into the house she patted my bum, and said if you like we could masturbate together, I said no but im really tempted as im not sure about girl stuff at all.
Im confused though is it illegal is it wrong, is it an ok thing to do, do others do it, or have done it,
Please help as i know shes gonna suggest it again.