i would definitely choose a thicker yarn, Ive made a few pairs myself, just hiking socks not hose (yet) and the first pair i made was good until both the heel and toes wore out completely, but i was just using a standard yarn that i had laying around. for my second pair i got a heavier more appropriate yarn and so far they are great! so sings of wear, and i can wear them a few times and still feel like new. also not sure what method she is using to make the socks but i would suggest to her that she use the 2-at-a-time method. for this you use one really long circular needle and make both socks at the same time, and this way they both are done at the same time as well are guaranteed to be the exact same size! there are many books available on this method. but either way I'm sure you'll have some great looking and feeling hose in the end.