Re: seperation anxiety
Just remember, the child belongs with parents, not grandparents. Grandparents are often too lenient for some reason. It is better for you to have seperation anxiety and back off a bit than for the grand daughter to wish she could stay with grandpappy.
From the other side, I have 2 step children. Grandparents on natural father's side were always stepping in (not natural father, mind you) and taking kids side. Made it tough for discipline. Both moved out when 17. Grandma took them to her house with grand promises. Daughter is now 23, son 21. Both are starting to come back around and grateful for our stand and resenting Grandma.
Make sure she knows you love her, help her mom and new dad out anyway you can, but do not get between them because you miss and love the grand daughter.