There’s a lot of things to consider.
Practically and legally, there are different ways you could have care of the child.
You could foster the baby. This brings ongoing support and supervision by the LA and you would also be paid an allowance as foster carers.
You would have a social worker as would the baby.
There’s benefits to this as you have access to funding and training but the child would remain a child in care unless they ever returned to mums’ care.
The LA are unlikely to want a long term fostering arrangement from birth. If there was little chance of the baby being able to be with parents then the LA and the courts will want permanence secured for the child.
If they were considering you as long term carers then they would likely push towards a special guardianship order. You would have PR but your daughter would also retain her PR.
There’s also a child arrangements order but again unlikely to be the choice of the LA and the courts.
Ok so other things to consider.
How will your relationship with your daughter and wider family be impacted.
What if she’s not allowed to be alone with the baby. Family time, birthdays, Christmas, holidays etc all need to be thought about.
How often do you all spend time as a family and how would this be impacted with you having care of her child.
How would you feel about managing contact potentially with dad as well?
Can you hold firm and manage conflict with birth parents? You’d have to choose the child every time.
Does your daughter need you? Does your priority need to be keeping her safe because you may have to choose between them.
Is it possible for your daughter to raise the baby with your support if she agrees to give up the boyfriend?
How old are you and how is your health? Can you commit to raising this child into adulthood if needed?
What’s the general family situation? Is there trauma and conflict. Honestly, would this baby be better off being adopted to strangers if your daughter cannot care for them. It’s not always the best thing for family to have care of children. Kinship care has a number of downsides which often aren’t discussed/explored enough.