Need GIFT IDEAS!!!!!! Please Help!!!

I feel bad saying this, but this is my situation....I`ve never known anyone that had/celebrated a quinceanera before, but I am now in a serious relationship with a guy from d. R. And his baby sister is turning 15. He invited me to her church service and party and I am going to meet his mom for the first time (really big deal!!) Anyway, I need advice about what an appropriate gift is for me to get her. I`ve met her before and we are starting to get kinda close. I was thinking jewelry; like a gold braclet or something, but my friend advised me that the typical thing to give someone for their 15th bday is money???? please help, I don`t want to look inappropriate and like an outsider; they alreay changed the church service to be in english for me bc I dont speak spanish! Yeah I know!!