If all else fails, I've read that the stuff in the link below works well.

Here is a link that might be useful: Ink Lifter

I have laminated posters at school, and hair spray works for them.
Sammy

Rubbing alcohol applied to a q-tip.The reason the laquer hairspray works is because of the alcohol content.I hope that the sofa is a light color.Tandy sells leather dyes online if she needs to touch up after she removes the ink.Unfortunately anything that removes ink will also remove dye..if she bought it from a reputable dealer,maybe she can get a professional to remove the ink.A high end car dealer in her area should be able to give her a name.Good luck.

Definitely what cupajoe said. My seven year old wrote all over our white Natuzzi sofa (black ink) on 3 different occasions at ages 18 months, 2 and 3 years of age. The rubbing alcohol and the qtips worked great, although it did take some repeated applications. It looks a bit splotchy at first, but then I cleaned the whole sofa off with a good wipe off of diluted Murphys soap and a microfiber cloth and it looked like new. Kids and pens are a bad combination, but boy can kids find a pen, even in a child proof drawer. I feel for your sister, hope it works out for her. Was she able to get it out? I'm a firm believer in white sofa. We have a brown leather sofa now, and I realize that if it were to get a stain the dye would really show altered in the brown. Let us know how it went.