Callistemon21
^He death is being investigated due to her being in a controlling and cohesive relationship with her husband^
Contact the police who are investigating your daughter's death and tell them you are fearful for your granddaughter as they have both disappeared.
Keep on until you get a result.
I agree.
What Iam64 said above and similar, too
Its true you can get a half hours advice free.
Contact your local Domestic Abuse helpline, mine gave me a list of solicitors who give half hour free time.
If you have anything in writing at all, like texts, take screenshots, the more hard evidence the better. (as you said "she sent numerous messages")
What about GD's school? Did GD or DD ever say anything to them?
I'd go to my MP, too.
All the very best x