She does! Finish, that is, not run out of yarn, although it was certainly close towards the end. If I had an overflowing basket of these yarns (or even just another two yards of the khaki, white and the lightest blue) I probably would have done the last few stripes differently, but I'm still quite pleased with this tidy little jacket. My cousin has a great deal of experience in designing clothes, and I was sorely tempted to gift this as an amoeba without sewing up the sleeve seams, just so she could see how it looks before hand. I will admit that it makes a much better presentation with all parts properly attached.
I couldn't find a lot of information about the best way to seam together perpendicular pieces of garter stitch, so I ended up just trying a bunch of things until something worked. The first thing I tried was stitching right behind the cast on row on the back, but because the stitching resembles a knit stitch it appeared as if there were two rows in stockinette right at the transition. I was worried that the seam would get bulky if I hid a knit row with the cast on edge, but the yarn is small enough that it didn't make much of a difference. If I have something critical to add before I find buttons I may post a close up of the seam, because I am very proud of how they turned out. If you're impatient you can just poke around on my Flickr page (click on the picture above).