It's a beautiful girls' favourite bag这句话对吗？

同意yaoyayaoya
语法没错,但表达不太正宗

不太好,it is a beautiful and popular bag for girls.

有歧义，那个漂亮的可以修饰包或者女孩，改为It's the favourite bag of a beautiful girl 相信我

不是很好吧~~
可以改成是:It's a beautiful bag which the girl loves.

不对
翻译为：这是一个漂亮的女孩喜欢的包。
该为：
This is a beautiful bag which girls like best.

不对的塞...
可以考虑
It is the bag that every beautifu girl loves...