So the $750/month is a calculation of cash flow... not savings. The monthly savings would be figured on the interest... not the principal. You might get her to play around with a credit card interest calculator:
http://www.consumercredit.com/CC-interestCalc.htm
It will give her a real picture of what it costs to carry a balance on a credit card.
I keyed in a $10,000 balance at 24% APR with a 4% or $75 minimum payment and the results showed that it would take 9.8 years to pay off with an interest expense of around $8900!!! $10,000 worth of retail purchases ends up costing almost $19,000! If the rate is 29% then it would take 12 years with an interest expense of almost $13,500!!! Meanwhile her money sits in the bank earning 2%. The smart thing to do is to write the big check and cut up the cards - then bank what she was sending to the credit card company. Assuming the interest rate is 24% with a savings interest rate of 2%, she's getting a 22% return by paying off the balance. Now if you offered her a guaranteed investment return of 22% I bet she'd take it!
The biggest thing to watch out for right now is that credit card companies are jacking up everyone's interest rates for no reason. You can be a perfect payer and get a notice that your rate has doubled. Send her this:
http://ezinearticles.com/?Default-Credit-Card-Interest-Rates-to-Increase-Across-US-By-Mid-May-2009&id=1988524