I don't yet own any lovely Blythe dolls; hopefully that will change come holiday season! However, it has recently come to my (apparently very slow) attention that Blythe dolls are actually larger than Pullip dolls, counter to what I thought for the longest time. Blythes are not so skinny, have a bust measurement approximately 1 cm larger, and generally need a length adjustment for torso, pants, and sleeves.
Accordingly, if you plan on making any of these patterns for Blythe dolls, you have a few ways of making them fit.
1. Don't modify them at all. Knitted fabric is stretchy. If you are afraid to experiment with your knitting, although I encourage you to try especially with such a small project, don't worry about it! Just leave the snaps off the back of the sweater and don't worry if it closes. Just have the open side on the back of your dolly and the camera won't show it!
2. Size up your needles and/or yarn. If you size up the needles and yarn, but not by much - say, using a 2.25 mm needle instead of a 2.0 mm needle, or use sock yarn rather than crochet thread, you will probably achieve the size you want. Do keep in mind, however, that if your gauge goes over about 9 stitches per inch, you are going to get a significant size increase. You can still use an item that is too large, however, if you are not OCD (it depends on the difficulty of the finishing as to whether I am) - just sew on the snaps to overlap in the back. You can also just pin the overlap on the doll and hide this with photographic magic.
3. Keep going after the increases are supposed to end. Probably the most difficult technique of the 3, because you'll have to do a little bit of compensatory math, this is the one that yields the best results. If you have any experience knitting, or are good at math (unlike me!), you might feel perfectly comfortable doing this. Most of my patterns have repeating increases - such as the raglan increases of 8 stitches per row. Instead of stopping at, say, 72 or 80 stitches, do one more repeat of the pattern's increases, and end with 80 or 88. Then, just be sure to factor in these extra stitches when you divide into fronts and backs. This may result in more positive ease (the garment is looser) than you intended, however, since this will add about an extra 2 cm to the garment. However, this is my preferred method because many Blythe enthusiasts dress their darlings in looser clothes than I usually style for my Pullips.
The main point would be to experiment. You aren't using much yarn and it will make you a better knitter. If you have a beautiful masterpiece that you messed up or just can't get to fit your doll, try bending a tiny hanger out of some jewelry wire (or not) and using the sweater as a Christmas ornament, cubicle decoration (brag about your leet knitting skillz!), or gift tag. People fawn over miniatures almost universally.