When I read your post It took me back, I could have written it over 8 years ago.
My DGD is 8 this week.
My DD fell pregnant when she was 15 and gave birth two days after her 16th birthday.
I think there is a possibility that this pregnancy was planned. I would try to find out who the father is. If she does not know when she got pregnant then they had sex on more than one occasion and this could be an on going relationship but she is trying to protect him. Try to establish if it is someone of her age and not a completely inappropriate relationship.
In my DDs case the pregnancy was planned, mostly instigated by the DF as his mother had abandoned him at birth and he was adopted. He wanted someone to love of his own flesh and blood. This did not stop him from abandoning his own DD before she was born.
I felt as you do about not wanting to be a mother to my DDs baby. I made sure this did not happen.
DD did not go to school during her pregnancy and we tried some courses set up for pregnant teens, however these were aimed very low academically. DD said that if you could read, write and count, and your parents were not in prison, drug addicts or alcoholics you would feel very out of place.
We decided to HE and the school allowed her to sit her GCSEs with her previous classmates.
I found it very difficult to get advice and support as it was felt we did not need any as I was capable and willing. There are charities that give support to prevent young women terminating, but if they have already made that decision they are not interested.
Well to cut a long story short, she had a baby girl and I helped her and advised her, but I did not take over. My DS is less than two years younger so I did not need another baby.
I will say that she did much better than anyone would have thought. As she was living in my house and only had to look after her baby and not worry about all the other aspects of running a house, it was not as hard as you may think.
If money is an issue she will be entitled to benefits.
8 years on and my DD is self employed, successful and excellent mother. Soon to be married to her lovely long term partner.
The hardest thing about it all has been the opinions of others who make judgements.
I think my DD was a lot more grown up for her age, than your SDD sounds, but she will grow up very quickly.
I wish you luck.