They made you the child's godparent for a reason. I would ask her parents if they would be offended or even mind some intervention on your part to try to help them with this troubled teen. Maybe tell them some things you are thinking of doing or saying to her and let them approve or disapprove.
Remind them that they did make you her godparent and that you are more than willing to try and fulfil your role. If they get offended in you asking, then there is nothing you can do, but watch the disaster unfold.
I have a cousin in another state that has had enormous problems with her son. He's done so many things to break the hearts of his entire family. I wrote her a letter after I heard about some of the problems and asked if she wouldn't mind me writing to her son and trying to help in some small way if I could. She was more than willing for me to help out in any way I could. After three years of sending him notes, cards, emails, and letters he's come around a little. I can't take any credit for his recovery, but his mother, father, and grandmother are happy I loved them and him enough to offer him encouragement.
Make clear to her parents that you aren't judging them or their efforts. Make sure they know you just really want to help if you can. Sometimes kids just need to know that even people that don't have to really love them and believe in them.
My brother's and I never gave my mom much trouble like you speak of, but we were a little apathetic. She found us the crappiest jobs she could find to instill in us a desire to do well in school and thus go to college. My brothers worked at a factory in a very hot paint room during the summer. The one brother also worked for a pet store and his job was to clean the kennels and fish tanks. We also worked at a peach packing house during the summer...and that was grueling. It would sometimes get to 105 in the warehouse. We would come home dripping with sweat and exhausted.
All of us went to college and have good paying jobs now.
Right now she does not see the need for school. She needs to understand the value of an education.
I would go to the local library and get your hands on some Career Choices curriculum...maybe her high school has some you could borrow.
She needs to figure out what she's going to do with her life.....what does she want to do for work? How is she going to support herself.
Have her investigate what that kind of job requires as far as an education. Then have her investigate the salary she can expect...benefits and so forth.
Then have her research the cost of living in the area she wants to live in. See what the typical utility bills are, what is insurance, how much do groceries cost....
Have her keep a notebook with all the information she finds out....
Send her on field trips to go grocery shopping with a limited amount of money...let her go with you and see how fast it spends and how long the groceries last. Have her shop for things to make a home...sheets, towels, cleaning supplies,
I would go around your house and make a list of all the basics to get started in a home...then have her go and price this stuff so she can see how much money she needs just to get started.
Have her look at your pay check...show her how much the government takes and so on.
Then have her pick out a home...what does it cost. Explain to her how mortgages work, what a credit history is, what her payments would be, what her insurance would run, what maintenance costs would be.
Then have her sit down and make a budget. There is a very inexpensive bit of software called "Budgets for Dummies"....she could input her salary, expenses, and so forth to see if she could make it and have the lifestyle she wants.
Most kids just don't understand what it takes to make a living. They don't understand how to budget. They don't understand that they can't have everything under the sun with a waitress job at Chili's.
She needs her eyes opened.
You might even be able to get a financial planner on board to help explain to her what she can expect to do if she doesn't even have a high school diploma. Then what she can expect when she is old enough to retire. Let him show her how far her money will go and what she can expect to do with that money.
Maybe even show her what an apartment paid for by tips from Outback will pay for. Take her to some apartments, have a realtor show her some low-income housing and then housing that is moderately priced to see the difference in what an education can get you.
She needs to see what she's aiming for now, what she could have with just minimal effort, and what is possible with some effort, planning, and goals.
Could a boy be her problem? Make sure that some kind of love issue isn't causing her to want to quit. Is she interested in an older boy that isn't in school?
Who are her friends? Are any of them drop-outs?
Good luck with this issue. I will pray for both of you that you can some how get through to her.