I will say that sometimes no system does much to help. My sister is dyslexic, and phonics won’t do much for someone who cannot see any difference between the printed words ‘god’ and ‘dog.’ Understanding the concept that they are different things is great, but does nothing to change the fact that either word is potentially a typo to her. One-size-fits-all solutions always have a human cost; this is the sin in socialism.
Seriously....Does whole word instruction make sense here? I don't think so.
This is my speculation:
Your perfectly normal and very intelligent sister was exposed to whole world instruction in the beginning. Being bright she may not have had to much trouble learning the shapes of the first 300 words or so, and then hit a wall in her ability to memorize the shapes of the words. At this point, failure, fear of reading, and shame sets in over the next year or two as she begins to fall behind those children whose parents who afterschooled their children with phonics. By 5 or 6 grade not only is remedial reading needed but physiological support as well.