Loft offers curvy fit pants (their “Julie” cut) up to size 18 and in petite. However, they have a plus section that goes up to size 24 although those don’t appear available in petite. I’m a big fan of Loft pants for quality (some of their sweaters get pilly quickly though). Different style are just naturally curvy with a smaller waist and wider in the hips so your friend should stop by a Loft store to try some on. I’ve always had better luck with pants that have some pleats at the waist and taper to the ankle. They seem to give my ample butt and hips a little more room. If your friend can find a sales rep familiar with the different cuts of pants, that could make her search more fruitful. Good luck!
eta: I also have good luck usually at Talbots but I generally shop online there.
" I object to violence because when it appears to do good, the good is only temporary; the evil it does is permanent." Mahatma Gandhi
"This is the ultimate weakness of violence: It multiplies evil and violence in the universe. It doesn't solve any problems." Martin Luther King, Jr.