when i used to knit with my mother we could use the same wool (yarn) needles, pattern everything but mine would be stiff as a board hers nice and floppy.
i used to pull the wool too tight when knitting. is crochet anything similar? is there a part on the pattern that says the scarf should be a certain width?
if you are pulling too tight it will be narrow and stiff.
on the pattern it should say what guage of wool to use, if you are using a pattern that is.