Regarding the heartburn - I've never had heartburn in my life and started to have it about a week into the cleanse. It disappeared several days later. There are two questions I would ask your friend:
1) Is she getting ALL the pulp out of the lemon juice? In my ignorance, I think I left a little in there and this may have brought on the heartburn (i.e. firing up the digestive juices without anything for them to digest).
2) Is she drinking the stuff right before bed? I found drinking it too close to bedtime tended to bring it on too.
That said, my heartburn did go away and hasn't reappeared.
Encourage her! It may just be a detox symptom too, she should at least tough it out for a few days.