My youngest graduated college this spring, and has been working at a great job since June. While in college, she had a few part time jobs...more than a few credit cards...and a habit of paying late, racking up huge fees and interest rates.

Since graduation she's paid off and closed all of her cards except for 1 w/ a low interest rate and balance. her last debt was eliminated in early September. Her credit report, however, is jacked-up (her words).

How long after one pays off one's debts can one realistically expect to see an improvement in credit scores? She REALLY wants to buy a reliable car and move into her own place, now that she's making decent money, but right now it's not looking too good.

any good advice?

I am with AD on this one.

The best idea a young person can get is to never use debt to begin with.
Google "Financial Peace University for the next generation".

She doesn't need debt to buy a used car. And shouldn't go down that road.

check out dave Ramsey.
http://www.daveramsey.com/

I've fought the credit battles for going on 30 years, if kids learn the best thing is to avoid using it, they won't have to fight the battle in 30 years.
If she makes good money she can build up her savings for a decent used car in pretty short order.