IS MY older SISTER SLEEPING AROUND?need help?

my sister is older than me the second oldest in the family we have a very tight strict family. as a 16 year old guy i am allowed to do stuff my sisters cant. i go clubbing hang out late and all taht stuff till liek 5-6 in the morning. also my parents know i am cleaner tahn a new born. i have never smoked weed ciggerettes or drank. even though all my frends sniff coke and everything else. they let me cause i am so dependable and in a way my father being a very macho traditional man takes it ok for a guy to do this stuff but cannot accept his daughters to. i tell my dad everything from to drugs one time he called i was having and i told him. so yeah that is tha case my my dad cant accept my sisters doign the same. teh eldest one is in university studies hard rarely goesout with frends cause she knows her priorities and has a very nice boifrend. my second sister is the problem. she makes my parents cry. she goes out late no1 knows who shes with where she goes to, and was