At Body Central, buy one regular-price item, and get 50% off a second item of equal or lesser value via coupon code "BOGO". Shipping adds $5, or bag free shipping on orders of $50 or more. A couple of best bets, with prices after coupon:
Aeropostale offers its Aeropostale Women's Curvy Skinny Jeans in Medium Wash for $16. Coupon code "FACTORY30" cuts it to $11.20. With $7 for shipping, that's $28 off list and the lowest total price we could find. They're available in sizes from 0S to 000L.
Orders placed by December 21 are guaranteed to arrive by Christmas.
Groupon again offers the Seven7 Women's Printed Skinny Jeans in Blue Chevron or Delilah Red Print for $10 plus $3.99 for shipping. That's tied with last month's mention as the best price we've seen for Seven7 women's jeans. (It's also a current low in any color by $19.) They're available in select sizes from 2 to 6 and petite sizes from 2p to 10p, although not in all size/style combinations.