I could have written this myself op. My dd had her first child, which she initially hid from us, at 15. She needed considerable support, which we and everyone else gave, but she started going out in the evenings. At first just Saturdays and I was happy to help out. Soon it was every night and she was so very horrible to us, that it was better when she went. She was so desperate to get away.
She just completely stopped caring for him because we were always there to step in. My younger dd was helping out a lot and I blame myself for the disruption of her childhood. After a blazing row, she left home, said she had been thrown out and was housed by a local organisation. She was pregnant again by 17 and again hid this.
She came back home to have the baby and the cycle occurred again. She did say she wanted him adopted, but childrens services asked my dh and myself. She left home again, taking the youngest with her. She could not take her eldest because we had a RO.
We were later called to take the youngest by the Police and asked to apply for an RO for him too.
I have brought up both boys. I don't regret it at all but it has not been easy. The children have not been the problem, it has been the father of the eldest who has taken me to court for contact which was an awful ordeal.
Your dd really does need to step up. The lies sound so familiar and it is shock after shock. Trust your instinct, even if you want to believe what she is telling you. She is putting her own needs and enjoyment before her child and it is fine because you are there to step up.
I know you will be worried about her giving up on her education but she chose to have her child and that brings with it responsibilities. She could go back to uni later on.
Please feel free to pm me.