In Catalan, the word for daughter is filla (clearly from the same source as girl in other languages), but the word for girl is nena. I don't remember whether la meva nena would be understood as my daughter or my girlfriend.
"A ta" is for singular, "ale tale" for plural. If you're talking to a man who has only one daughter with the specified qualifier you should use the former. For masculine nouns, the corresponding forms are "al tău" and "ai tăi", respectively.