From what you have shared of her behaviors it sounds like you are dealing with a child inside a young woman's body. I have shared my thoughts in our PM's but I did not want to leave your question unanswered on the board.

Complex PTSD is not just a one size fits all. There can be other challenges involved as I have mentioned. I think what she is trying to say is "I am too little to handle all this adult responsibility of knowing how to be a wife and a mother".