How to ask parents to go out for travel (16F)

eng is not my first language ,sorry

My cousin invited me to go to trip w her , i really wanna go since everyone go to travel to basically everywhere on earth except me. i study harder , i save up my money for this trip . When i ask my mom if i could go with my cousin, she always said no! And last time that i ask her she said to ask my dad(?) im not really dont wanna ask him much since he just brought me some essentials for my next school year. My cousin is always help me convince them to allow me to go with her, and her parents are gonna help me for the cost of the trip (so basically this trip is free) but my mom still said No because i have to go to my cousins house alone. But my country is still safe for teenage to go on plane/ train alone. Can someone help me since the school break is almost over next week is gonna be my last chance to go with my cousin. I hope they gonna say yes soon because I already ordered some dress for the trip

Thanks for advice , ^^