The treatment of expenses paid with distributions from Sec. 529 plans and Coverdell ESAs in the support test is uncertain because of the dual nature of these college savings vehicles and a lack of IRS guidance. The consensus among tax experts is that it is parental support, because the parent is the owner of the plan. It would be helpful, to your case, to make distributions to the owner, not the beneficiary or school.
References:
https://ttlc.intuit.com/questions/3402602-can-i-claim-money-from-a-529-fund-as-my-supporting-my-22-y...
https://www.savingforcollege.com/articles/the-impact-of-529-plans-on-claiming-a-dependent
