I don't mind. Go for it.
I'm sorry to say this but you can't give her permission. You don't own this, you said it yourself. Someone already posted this on tumblr(that's where you got it from I assume)
You should give a link to the picture you used.
I don't own it so I don't really care what people do with it. I just found the blank hair flip gif. and combined it with the words that I had seen on a still pic. I had found both on google image search so I don't actually know where they came from, there are versions of the same hair flip gif. everywhere.
Exactly you don't own it. Devaintart is an art website and posting things that you don't own is against the rules and one can get reported. I'm not saying this to be mean so please don't think bad of me. But you are new here and maybe your not familiar yet with our rules. You can post stuff like this but always provide with link to your image sources so there won't be any misunderstanding.