Poor dd and poor you, incest sexual abuse is an absolute mind fuck for the victim, it takes years to live life away from the devastation to the psyche.
Getting her into counselling, someone whom practices psychodynamic play therapy would be the branch to take.
Get help as hellsbells has suggested with the links that she posted.
Her poor scrambled head and heart will need a lot of help to heal.
She would benefit from re-parenting, so parenting her as though she is a 'toddler' in terms of imput, closeness and bounderies. Basicaly taking it back to before the abuse started. Making sure that you read to her at bed time, food is eaten together, doing crafts together etc. Making sure that she is out in nature, making bows and (not sharp) arrows, camps, foraging. Picking rose hips (for rose hip syrup) and blackberries (for a crumble or jam) and so on.
Basically overlaying her sence of self with feeling meaningful self worth. Connecting with nature is very theraputic, even just getting ones hands in the soil and growing things if you have a garden.
Giving her a really good diet will help as there are plenty of fruit and veg that will help with the production of happy chemicals. So 8 to 10 fruit or veg a day, cut down on refined food that does bugger all for positive mental health. Make sure that she drinks lots of water.
At night have the same bedtime routine that she had as a toddler, bath (with bubbles and bath crayons), book, reading to her whilst she is in her bed will allow her to feel loved and worth while. Stroking her head as you read if she will allow you to will sooth her. Maintain regular bed time and helping her to sleep well will reduce her stress. Pop a night light on if she sleeps better with one.
Most of all she needs love, nourishment and security of a child much younger than her.
Look after yourself also, it is really hard as a mum seeing your innocent child damaged in such a destructive and horrid way by a family member, the guilt as a mum in this situation is unbearable.
I hope that your dd can step onto a road of recovery, she is so immensely brave.
She is a survivor, 