If I am remembering correctly from my childhood, didn't Scooby Doo also have ghosts in the stories? What if that is what she is afraid of and can't verbalize it? If so, no "Monster Sray" will help, no matter how much glitter you put in it.
My son has not asked about monsters or ghosts, but if he did, I would attempt to comfort him with wisdom from the Bible (in much simpler words, obviously.)
I don't know your beliefs or if you even want to address this, but this is what my suggestion is for what it is worth:
I think your daughter is scared and she has every right to be. She has been taught something scary exists and it will take a while for that to be untaught and for her to feel secure again.
I tell my child, "When people die, it's like they are asleep; they can't hurt you."
Your daughter's need of security is paramount, so whatever your belief is, I hope she finds some peaceful sleep soon!!
All the best, Liz
P.S. This is my belief on ghosts, etc. if you are wondering why I tell my son that dead people cannot hurt him. Yes, I do believe that 1/3 of the angels that fell from heaven are alive and well and doing horrible works, but I think that is way too much for children to comprehend and need not be addressed. Their need is to feel safe....
David declares that man is not conscious in death:
"His breath goeth forth, he returneth to his earth; in that very day his thoughts perish." Psalm 146:4.
Solomon bears the same testimony:
"The living know that they shall die: but the dead know NOT ANYTHING." "Their love, and their hatred, and their envy, is now perished; neither have they any more a portion forever in anything that is done under the sun." "There is no work, nor device, nor knowledge, nor wisdom, in the grave, whither thou goest." Ecclesiastes 9:5, 6, 10.
When, in answer to his prayer, Hezekiah's life was prolonged fifteen years, the grateful king rendered to God a tribute of praise for His great mercy. In this song he tells the reason why he thus rejoices:
"The grave cannot praise Thee, death cannot celebrate Thee: they that go down into the pit CANNOT hope for Thy truth. The living, the living, he shall praise Thee, as I do this day." Isaiah 38:18, 19.
Psalms 6:5; 115:17
"In death there is no remembrance of Thee: in the grave who shall give Thee thanks?" "THE DEAD PRAISE NOT THE LORD, neither any that go down into silence."
Peter on the Day of Pentecost declared that the patriarch David, who was righteous before God "is both dead and buried, and his sepulcher is with us unto this day." "For David is NOT ascended into the heavens." Acts 2:29, 34.