What do you mean by "plaster board walls"?

Gypsum drywall (Drywall is actually a trade mark IIRC)?

Since there are always studs on each side of a window (possibly multiple in a weight bearing wall) is is not usually very hard to place drapers rod fasteners into the studs.

Anyone think a hilti toggler might be good if she wants to spread the brackets out past where the studs would be?

Here is a link that might be useful: Hilti toggler

If you are past the studs any number of expanding anchors can be used.

Molly fasteners still have one of the larger footprints behind the wall since they expand in four directions.

A lot depends on how heave the rods and draperies will be.

if they are very heavy (say over about 50 pounds) you may need to install blocking behind the finished wall fastened to the studs and then repair the wall.