I have a friend who, 5 days after payday has no more money left, and keeps on piling on her credit card debt. How do I advise her?

It's very difficult to help them, especially if they do not think they have a problem.

I think this kind of cases, they are deep in denial and have another serious underlying problem that could be more psychological (could be depression, can't handle the stress, could be drugs, gambling, abuse at home). Usually, the spending is a means of escaping to avoid facing that problem.

A simple way is to help her build the current debt picture. Ask her to apply to see her current credit rating report from the credit bureau. I just applied the other day n paid 6.42 to see mine. It has quite a bit of details, and can present the consolidated debts (from licensed institutions) as of the last mth ending balance. The bad part is it doesn't include ah long and family/friends.

Excluding mortgage, if the total debt balance now exceeds

A) 2 yrs salary, it's pretty much a gone case, go file for voluntary bankruptcy.

B) 1 yr salary, go take consolidation loan to bring the debt immediately down to 4-6% interest per yr, n seek credit counselling. Best to chop up the credit cards, and focus on pay off the loan.

C) less than 3 mths salary - this is still a very fixable stage. My suggestion is to cut the credit limit voluntarily, I would suggest 30% of take-home pay (but only works if she thinks n agrees she has a problem). Cancel all the cards if she can.

DAYUM! What on earth is she spending money on? Being able to spend a month's salary in 5 days is an incredible feat IMHO.

It sounds like she has a pretty serious spending habit, and if it's for non-essentials, then she really needs to relook her spending habits, as you have rightly pointed out.
But more context is needed here. Does she have a big financial safety net in the form of rich parents? I once had a girlfriend who spent extravagantly and would go for a few hundred dollar hair salon visit whenever she felt stressed at work. And given the job at that time, we were probably super stressed everyday XD

IF however, she does not have a financial safety net, then the spending habit will catch up to her especially when the credit card companies start demanding for repayments.
It's great that you want to knock some sense into her, and you probably have told her it's not such a great idea to spend beyond her means. If she was a good friend of mine, I would delve deeper into the root of why she is spending so much. Is it insecurity that is leading her to buy expensive items? Is she trying to appear rich in front of her friends?
Identifying the root problem here would be a good start.

She need to know a guy she love enough to change her mindset for her future.

Preferably, the guy is
1. Fit
2. Kind
3. Smart
4. Always there for her to remind her
5. Good with money
6. At least a bag of gold.

That is if she could not get finance awareness for the future herself.

The rest will be her Destiny.

Use credit cards to earn cashback, not to borrow money. Advise her to save, not to overspend. Spend within her limits. She may need to go for financial counselling.