that will means: "you are already cute(enough)" you can say: 妳真是超美的! 好漂亮喔! 真是個美麗動人的新娘! ..等等 and 好幸福,好棒喔! .. 等等

could， but only to young girls. do not ever say that to a boy, some could get annoyed by that, but i would say most of girls will love to hear that .

bien sur~ mais vous pouvez dire 你很可爱 il n'y a pas de 了 parce que 了 dans le Passé parfait seulment

Of course you can say so,it mean one is very lovely very cute.Adults also can be cute~^-^

you can say"你好可爱啊！”“你好漂亮”“你们好相配”！！