My 22 year old child lives away and attends college full time. She pays living expenses from a 529 college fund that we disburse to her monthly. Does that count as her paying 50% of living expenses or us paying?
Good question. Short answer: that is support provided by you.
"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". Reference: http://www.thetaxadviser.com/issues/2010/aug/nichols-aug-2010.html
You should treat it as support provided by you, because "everybody does it". You are on firmer ground if the funds are distributed to you, rather than her or the school (you are the recipient*). But I would not give up the tax advantages of distributing to her, when appropriate.
For more on 529 plans, see https://ttlc.intuit.com/questions/2662573-where-do-i-enter-1099-q?jump_to=answer_4402991
*For 529 plans, there is an “owner” (usually the parent), and a “beneficiary” (usually the student dependent). The "recipient" of the 1099-Q can be either the owner or the beneficiary depending on where the money was sent. When the money goes directly from the Qualified Tuition Plan (QTP) to the school, the student is the "recipient".