I've not had an Abdominiplasty, but I've had Liposuction and was really pleased with the results. However, I've not had children, so don't have that overhanging "apron", often associated with pregnancy.
Being an avid fan of all the cosmetic surgery shows on TV, I seen many procedures carried out. I believe when an Abdominoplasty is performed, first Liposuction may be performed, then the underlying muscles are repaired. (During pregnancy, the muscles seperate to accommodate the growing bump and often don't come back together properly).
After, the loose skin is pulled towards the bikini line, the navel is left intact, on a "stalk" and just pulled through a new hole, which is cut in a new position. Excess skin is then cut away and then what's left is attached to it's new position. They join along the bikini line, so scarring is hidden. There will be a long horizontal scar, which travels from hip to hip.
From what I've seen on the documentaries, the results are usually very satisfactory, but ensure your friend finds a good, reputable surgeon, who has vast experience of this type of procedure.