My 17f sister almost 18 wants to marry someone 9 years older.

My 17f sister almost 18 wants to marry someone 9 years older. This counts as pedophilia right? Also family members are considering it as her father is a alcoholic as he didn't ask for dowry, like what the f*ck. I am 16f , what should I do ? I told them it's a bad idea and they shouldn't go for it. I said she is way too young to decide. My mother said what if she runs away and get married? . It's so stupid. They are saying who would marry her? Like man. A lot of boys would . There's no scarcity for men and she's pretty. But poor. I suggest her getting a job , but idk if she cares , she trusts ppl so easily , ahhhhhh. And plz don't say give up or you can't do anything. Idc if everyone hates me , she is my sister and I do not wish to regret anything. Everyone already thinks i am spoiled anyway. I need genuine advice plz.