I would start with the figure and bed posed the way you want it in frame 1 then do not change it. However if you do this ensure that "Drape from zero pose" IS NOT selected in the simulation settings.

Then, still at frame 1 position the blanket horizontally over the figure. Suggest 3" above the highest point of contact.

Ensure that the blanket is set to collide against the figure and the bed. If the hands are not going to be seen then set them invisible before doing the simulation. At worst they will cause poke through or snagging, at best they will just slow down the calculation. Same for the hair.

If the pose results in the blanket sliding off then position it very close to the first point of contact then select the adjacent vertices in the blanket and assign them to the constrained group.

Give it a go, post your results and we can go from there.

Good luck :)