So I did what I had to do... ribbit. My lil sis is only 5'2", and the scarf was about to be 5'11" or so... Anyway, I adjusted the pattern a bit and now it's much better, with just a smidgen over 3' stripes. I'm about halfway through stripe seven. I'll post a pic later when I'm not so lazy.
As for the baby sweater, it now has two sleeves (just imagine!) and has become a bit of a pain to tote around. I'm thinking I'll just work on it at home and take the scarf with me, although soon that will be too long to be portable and I'll have to start something else... Don't want to mop the floor of the subway or anything! Socks maybe?