Hi Cyber,
It is NOT a matter of 'paying' for her past deeds. They are paid for. Period.
HOWEVER, consequences are a different matter. This is the first thing. For example, when my oldest son was young and we gave him his first two-wheeler (bicycle), I instructed him not to ride on our hill, but I would take him to the school yard later in the afternoon to ride.
He disobeyed and tried to tackle the hill, which was quite steep. He crashed. He tore himself up and was in quite a bit of pain and also ruined his brand new bicycle. Neither of those things was a punishment. Just a consequence. Punishment was our refusal to fix his bike, which was beyond repair anyway, or buy him a new one.
If what is happening to your friend does not fall in the category of consequences, then there is something else that would apply to her as a Christian, and it is best explained by Joni Tada in her book "One Step Farther." There she talks about if a jeweler has an incredible diamond, better than all the other jewels he has, he does not display it with all the others. He puts it on a field of black and shines a light onto it.
God's grace is that diamond. Sometimes He allows our lives to become fields of black in order to show the world what His grace is like. If we suddenly became immune to problems when we became Christians, then we would all become Christians for our own sakes, to be free from our problems! However there are times when Christians seem to get the worst of things, and it is then -- in the crunch -- when the world is watching that they either see God's grace in our lives.....or not.
So whatever is happening to her, if you know any female friends of hers (or if you are a female, I can't tell from your cyber name), you need to stick close now and walk with her and pray with her and not be like Job's 'friends', no matter how long her time of 'black' continues. God is not forgetting her, not making mistakes. Help her along if you can. You cannot walk for her, but sometimes it helps if you can walk for a bit with her.
I'm hoping someone else can give you the Scriptures. It is almost 3 in the morning here as I write this. I got up for a pain pill and it is starting to take effect and I need to go back to bed now.
God bless.
Helen