Moira Prophet was one of Prophet's three adult children who had filed a counter petition in response to Murray Steinman's attempt to control the spiritual leader's legal, financial and medical affairs. He is a vice president in the church.
Court documents say Prophet endorses Steinman's guardianship petition.
Moira Prophet's decision, filed March 4 in District Court at Livingston, leaves two of Prophet's adult children, Sean and Erin, seeking to become their mother's conservator and guardian, respectively. Prophet's other adult child, Tatiana, has not participated in the suit.
Prophet, 59, announced four months ago she suffers from Alzheimer's disease. Memo: She is a former president of the church and plans to step down as its spiritual leader sometime this summer.
Also, the church filed a "statement of interest" in court earlier this month requesting notification of any orders issued by District Judge Nels Swandal affecting the ailing spiritual leader.
The statement requesting the action said Prophet is a "person of monumental importance" to the church.
State statutes covering guardianships allow for government agencies planning to pay benefits to "incapacitated people" to be listed as interested observers.
The church said it has similar plans to provide medical benefits and provide Prophet with housing and an annual pension of $67,000.