Most sock patterns with the usual 64 stitches for women assume a foot/leg width of 8 inches. In my experience tightness around the foot isn't as common as tightness around the instep or looseness around the leg ( at least in my family). I highly recommend this book
My husband has big and wide feet but a normal leg, for him I cast on 68 on 2.25 mm needles and when I do the heel shaping, after picking up stitches, I don't decrease back to 68 but keep a few more stitches to accommodate his high instep and wide feet.
Most handknit socks fit best with negative ease — that is, you knit them a bit smaller in the circumference than the intended foot.
That is about 90% of total is the guideline suggested by Knitty's Sock Formula. I've knit all of my socks to that percentage and have been very happy with the fit.
Best really is if you can get measurements.
Also beware of lots of cables, they make a tight unforgiving fabric and you might want to go up a needle size or cast on more stitches.
Foot circumference on the chart is the measurement of the foot for a "normal" width. Calculate 90% negative ease to find the circumference your sock needs to be.
My foot is US size 7 and I wear a wide in some styles, so I need an extra half an inch from what the chart says.
My sister has a 'regular' width foot, so I'd use the numbers directly from the chart and would adjust for negative ease to choose her sock's circumference.
And to better assure a fit when you're sort of guessing with this pair, consider adding a couple rows of elastic knitted in at the cuff.