All we can do is offer advice. Remember, you give advice to help the person and not yourself. But I know how you mean. It'll be nice if we see her improve, so hopefully she'll listen to some more cronstructive comments and implement them into her poetry in the future.
That's why you dont tell them how to write, you should just direct them in a proffesional point if you know where I'm coming from. For example. if someone were to write about "Love" you couldn't say "hey, no this is not a good theme and it doesn't work and I dont like it because... etc." but you can however comment on such things as flow, language, dailogue, technique and such.
Welcome to the life of a critic. You see, some people have the mentality that when someone has reviewed their poetry, they think "I did not ask you to that you didn't have the permission". Rather they prefer "Wow this poem is amazing it really spoke to me I love it!" poetry isn't like that. I hate those comments as poetry has depth, and so should it's replies.
Well, now I dont mean to be harsh, but this is the truth; those who do not accpet constructive crit. cannot be called artists in any shape or form. As a writer you want to imprve and get better, you can only do that by learning, and through reading reviews you improve!