Either could be used depending on context.
For example, "I said goodnight to Mary" or "I said goodnight and Mary said goodnight, too."
The first sentence implies that I directed my words toward Mary and not toward someone else. The second sentence means that both Mary and I said goodnight, without specifying to whom we addressed our words.
You would generally say goodnight to someone.
You would rarely use the word "too" after goodnight. If you did, it would mean "also."
In Polish, you say "dobranoc" to wish someone goodnight.
In Zulu, you would say "Lala ngoxolo" to wish someone goodnight.
In Bicol, you say "Ma-aram na pagka-anggay" to bid someone goodnight.
In Flemish, you can say "goedenacht" to wish someone a good night.
In the Solomon Islands, the most common way to say goodnight is "goodnight" itself, as English is one of the official languages. However, in the local Solomon Islands Pijin language, you can say "gudnis" or "nait nait" to bid someone goodnight. These phrases are commonly used to wish someone a peaceful night's rest in the Solomon Islands.
Well, I'm a girl, and I would say that some of the best ways to say goodnight to girl depends whether you're saying it to her or texting/messanging her. If messenging her, then don't say it too late, and if saying it to her, then a simple goodnight is all it takes.
In Berber, you can say "tanemirt" to say goodnight.
You can say "lafi" to say goodnight in Mandinka.
goodnight
goodnight!
"Goodnight".
In Fulani, you can say "Jaama wolof" to say goodnight.