The actress is being held at a Ventura psychiatric facility following her detention last month by Ventura County sheriff's deputies after she set a fire in a Thousand Oaks driveway.
Bynes' parents have been attempting to win a conservatorship for their daughter so they can control her affairs and medical treatment.
On Friday, a judge in Ventura County extended Bynes' mental health hold by 30 days and gave her mother some temporary conservatorship powers, according to People.
In seeking a conservatorship, lawyers for the parents described Bynes as using drugs, consumed by paranoia and having spent $1.2 million in just a few months.
Bynes' parents said they were "deeply concerned" that their daughter poses a risk to herself and others and that her behavior has been fueled by paranoia, drugs and an obsession with plastic surgery.
Rick and Lynn Bynes, in court papers filed by attorney Tamar Arminak, said the incident in which the 27-year-old actress allegedly set her pants on fire in the driveway of a Thousand Oaks home is the latest in a series of episodes that illustrate why she needs a conservatorship.
In court papers, the actress' parents described their daughter as "appearing to have a substance abuse problem" and being "extremely paranoid about being watched, including at our residence."
"She would cover smoke alarms with towels, tape windows shut and cover her car dashboard with cardboard and tape out of fear that cameras were watching her from inside these places," according to the documents.
In addition, they said it appeared she has "body image" issues and is obsessed with the idea she and others are "ugly," noting she called a young niece "ugly" on Twitter.
Bynes, her parents said, talks "incessantly about cosmetic surgeries that she wants" and they have "received large doctor bills." In recent months, since moving to New York, she has started spending large amounts of cash.
According to the filing, Bynes had about $4 million in savings but has spent about $1.2 million in a short time, with many checks written out to cash. In June and July, they say, she withdrew $100,000 from her accounts -- all in cash.
The parents are seeking control of her finances and medical decisions. The move mirrors that of Britney Spears' parents in 2008 after she exhibited what seemed to be erratic behavior. Spears remains under a conservatorship.
[For the record, Aug. 9, 10:52 a.m.: An earlier version of this article incorrectly said that Amanda Bynes had been detained last week by Ventura County sheriff's deputies.]