She’s over 21, not criminally insane, she earned the money, let her have it. If she blows it all, it’s her fault. If not, it’s her praise.
Conservatorships should end at 18, in rare instances a shared conservatorship between the earner and the trust until 21 (unless it is a tax-free trust for education – those have state rules). Her parents are afraid they’ll not get any more money out of her. My kids had a trust for college that I set up when they were young. At 18, they could choose university or trade school. Two chose university, one trade school and is now a carpenter and general contractor with his own company. Any leftovers after they graduated were theirs to do with as they pleased. My son chose to start his own business. The elder daughter used her leftovers to buy part ownership in a restaurant, the other daughter works in a big city trauma center in the emergency room and is using her leftovers to get her master’s. I’m rather proud of all of them.
The only thing I get is a free dessert at the restaurant, free (and very good) medical advice, and an honest estimate on contractor work on my home. Oh, yeah, the carpenters and such actually show up on time and do all the work on time and do it right, which I hear is uncommon.