Hmm from what you've told me, I would say either "She has cut her hair" (also "she has" would be abbreviated to "she's" when speaking) or "She has had her hair cut", simply because the following sentence is in the present (she looks beautiful). If the following sentence had been in the past (she looked beautiful) I would say "She had cut her hair" or "She had had her hair cut". There's absolutely no problem with using any of these sentences as far as I can see :)

I really appreacite your comment. It cleared me a little bit more my doubt. I already know the use of that sentence. Answering your useful questions, he is brazilian (so his language native is portuguese, but he knows a lot of English language, I guess therefore I used to talk to him everytime I can to improve my skills). That was an informal conversation that started from here: Me: She cut her hair, looks beautiful. He: She is amazing... so looking forward to see her close up... she cut her hair? no no... come on... do it better. Me: I'm sorry... I don't know how to say it... Her hair was cut? Hahah I'm sorry He: u told me i didn't want to help u out sometime ago... i'm just doing what u said.... nope.. try again.. Me: Haha you are so bad... I really don't know... Srsly. He: a tip... nobody can cut his own hair... so?? Me: She let someone to cut her hair? Hahaha ... It's tough He: it is still wrong... come on Me: She has short hair now... Jaja He: hahahahaha....hahahaha Me: Is that wrong? Haha He: no... it is right.... a lazy way of saying it... shame on u :( Me: Please say to me He: what would i gain from it??? ... she had her hair cut... see?? not so tough as u thought... u should've paid just a little bit of attention. Just kidding... Me: Mmmm .. That means "ella se cortó el cabello"? It's weird... I would never have been able to say it of that way. He: if u worked at a beauty shop, u could say: "i cut her hair"... but as a client, "i have my hair cut"... Me: That grammar "I have my hair cut" is kind of weird He: i know.... i thought the same for the first time As you well see, I looked for many ways to say it, that's is why this phrase caught my attention. Thanks a lot again for your response.

It really does depends on the context - this can affect the verb tenses used as well as other things. I know that I have used the sentence "she has cut her hair" before, when talking about someone even though they almost definitely didn't do it themselves. Can you give us a bit more of the dialogue that surrounded the sentence please? Also, is your friend a native speaker? I only ask because maybe he has learned set phrases, which is why he may not know that it's acceptable to say it in another way.