First and foremost - they must keep her on lead until the problem is resolved. To lose her could cost her her life on the roads, on a railway line or cause her to be picked up by someone unscrupulous whereby the owner never sees her again.
Next, is she spayed? If not that might account for her behaviour. There are scores of other reasons why she should be spayed too.
Next, your pal needs to start from scratch. Begin in the home or garden with some really nice, smelly treats (Google how to make liver cake). Call her and reward with a treat immediately when she comes. Do a few short sessions of this consistantly, say 5 or 10 minutes, every day. Don't do it for too long, she will get bored and switch off, it is then counter-productive.
Continue meantime walking her on lead - maybe use a long training lead and again call her and treat immediately when she comes. The trick is to make YOU more interesting than anyone or anything else in the world. Do this at first when you are sure there are no distractions in the park/fields and work up to doing it when there are (maybe get a pal with/without their dog to be a stooge). Be consistant, repeat, repeat, repeat. It's boring and arduous but it could be that or the dog losing her life if she runs off again.
Eventually your pal will be in a position to recall with the dog offlead in public. First of all do so without distraction and again, build up to off-lead with a distraction.
Lastly, tell your pal to consistantly use a WORD for recall, rather than the dogs name. She hears her name all the time, "Oh, Rover, your feet are muddy, Rover what have you got, careful DS, don't tread on Rover's tail..." and so this often becomes a bit like background noise to dogs. However, come or here, if associated with a treat, means just one thing... get back to owner fast.
HTH. :)