I thought that I would make her a simmilar blanket, designed for use on the couch. The twist it has compared to any other blanket is that it has a hood built in, kind of making it a huge hooded poncho. After starting the project I came across this couch dress, which is similar in function, but mine just has a hood to keep you as covered up as possible (and it's a bit cheaper too).
The only tools required are a sewing machine and pins, the consumables are cotton thread (colour of your choice, will be hidden) and the polar fleece material (step 3).
Step 1: Design
The original flag I made was 2m x 2.5m (roughly 6.5' x 7'), because this was about the size I thought I would be able to wave around reasonably easily. "Testing" of this prototype of the hoodie blanket by my girlfriend showed that it was an excellent size for convering two people up close on a couch, and convieniently fits a queen sized bed perfectly for use as a spring/autumn (fall) blanket. Therefore I'll stick with a 2m x 2.5m size.
The flag used an alternating squares pattern of orange, black and white. The squares were 500mm per side. This seemed to make a faily pleasing design, so I went for the squares again, but I'll choose some different and a wider range of colours. Allowing for a 1cm wide hem around each edge, the squares end up being 520mm each side.
At this point I didn't have a set-in-stone design for the hood, just a general idea that it should go on the centre line roughly one square in from the end. This way when you've got it on and lying down it will still cover you from head to toe.
The hood will be cut with the squares adjacent to it.