Mikel, if you want to try your hand first at an informal demand letter and only enlist a lawyer if you have to, here's a little format you can use.
http://forum.eastwoodco.com/showthread.php?t=6569&highlight=demand
Adding threats of the liens and attachments that will be filed if she ignores you will also get a lot of attention.
I wish all my customers treated me like FABO members do! I've had one bad check Harley parts client ($485.00 plus bank fees) from the Nashville area, and went with my 6'5 280 lb. enforcer -- Billy LOL -- just this afternoon to drop by a local bike customer's place to see if he was ready to pay for his chain guard he dropped off almost six weeks ago. But other than that, I'm knockin' on wood and considering myself lucky with this economy.
Forty thousand dollars plus interest and aggravation .... I feel for ya! Best of luck, and godspeed to her right foot as she drives to her bank to finally pay you.