Good Friend, Intimate Friend, Close Friend
noun, な adjective, の adjective
You have a good relationship with someone. This is someone who is your good friend or intimate friend.
なかよし
The readings are kun'yomi as you probably guessed from the hiragana sticking out, but that doesn't matter because you learned the kun'yomi readings already.
あの二人、仲良しなふりをしているだけで、本当は仲が悪いと思うよ。
I think they are just pretending to be intimate friends and they don't actually like each other.
先日、日本に住んでいる仲良しの友人から、メールが来ました。
The other day, I received an email from a close friend who lives in Japan.
あの子たち、ホントに仲良しだよね！
Those kids are really good friends, aren't they?