I do have a similar kid. Essay writing is like pulling teeth. For DS16 his problem is in creating content to write about and not about the execution. He has written only a few sentences on essays that teachers are expecting pages on because 'he has nothing to say'. First day of his gifted pullout in 4th grade and the teacher assigned a 'tell me about yourself essay' and my son wrote one sentence.
I have not had the same attitude but rather the reverse. Since he struggles to write essays, he couldn't possibly be gifted. He can't take the honors high school English & Social Studies because he can't write well enough. So he is stuck in regular English classes bored to tears with most the the material. Gets mad because he has to read the abridged version of the book. Thankfully this isn't necessary for math class, but it has hurt him in science.
It is important that your child is writing AT grade level. And you should keep pushing this because it will come back to bite you at the later grades. I don't have a lot of suggestions except to keep pushing. And if you can get her outside help in the meantime. What I've found is not a lot of people know how to help DS with the 'having something to say' part of writing.
