How would you "encourage" development and change in this person?

A colleague at work and his bipolar wife had one child, a daughter now age 30. They started off raising her as an achiever – music disciplines, bilingual school all of that. In her teens she got into drugs, altercations with parents and ended up leaving home for several months. She came back with a better attitude but it dissipated as familiarity with the good economic life settled back in. Gradually she began living in earnest as a “princess.” They were that glad to have her back again.

My colleague is the “breadwinner” for the household – he’s a professional and away from home a lot. The daughter attempted and abandoned two paths of training for her career. She finally realized she has aptitude and skill for very fine work – making jewellery and she has a job at an orthodontist lab. She doesn’t pick up more that 30 hours a week on the job and doesn’t want any other job. She let herself get quite overweight and lazy.

She now lives away from home in an apartment dad set up for her to the tune of about $10,000 and contributes $300 monthly towards her rent. She ran up her credit card to maximum and hasn’t even the funds to keep the interest on the card in control.

The dad has over a period of time come to see what the true picture of his daughter is. He has confiscated her credit card and strongly advised her to get a part time job to supplement the lack of regular work hours. She is holding on to her princess crown quite firmly at the moment.

Do you have any insight on how anything can be changed to mature her at this very late time without completely dismantling their relationship? P.S. The mom loves to shop too but her “swings” cause her to go back and forth between supportive of her daughter and seeing her as “fat and lazy”....