Hi OP, I hope it all goes okay with your daughter.
(Sorry if this is long)
I got pregnant at 15. I told my parents at nearly 12 weeks, they were obviously devastated but after a few days they came round. Their initial reaction was what I feared it would be, which is why I waited so long to tell them. Because of this, I'd like to think I would be extra calm and gentle should my DC disclose something like this to me.
But after that, my mum was amazing. Once she understood I would not terminate, she accepted my choice and didn't (at least to me) express any disappointment from there on. I actually think this was the single best thing she did for me at that time.
My mum even allowed herself to become excited at the prospect of her first grandchild, she took me out shopping for baby things and attended all of my appointments. She advocated for me and respected my decisions on what birth I wanted/how I would like to feed the baby etc.
Once my DC was born, she (and my dad) paid for everything and my mum cared for my baby whilst I went to school (Year 11). All I was expected to do was to go to school and then come home and look after my baby. Mum took care of most of the housework.
Looking back I can see how fantastic she really was and how it enabled me to bond with my son and achieve great GCSE results. I then went on to sixth form with my peers (DC attended a creche - under 19s get free childcare) and then I moved out of my parents home with my DC as I went to University (if you had a child, the loan company did not look at your parents income for grants/loans etc.).
I am now nearly 30 years old and my son is 14, I have a good job, I am married to a lovely man and we have two more children. My son is a wonderful boy and my mum loves him like her own.
I just wanted to share my story to give you some hope. It certainly isn't an ideal situation, but it doesn't have to be the end of the world. Life can be what you make it 