BEIJING -- Liu Xia has had enough.

First, Chinese authorities sent her dissident husband to jail for 11 years. Then they made her a prisoner in her own house after he was awarded the Nobel Peace Prize.

Finally, they jailed her brother -- also for 11 years. Fed up, she's now preparing a legal challenge against the authorities, her lawyers said Friday.

Liu Xia has authorized Beijing attorneys Mo Shaoping and Shang Baojun to represent her in suing Beijing police for placing her under illegal house arrest and to prepare a petition for her husband Liu Xiaobo's subversion case to be retried, Shang said.

Her brother, Liu Hui, has already filed an appeal against the 11-year prison sentence handed down to him earlier this month for fraud in a real estate dispute that the family's supporters say is meant as further punishment of the Nobel laureate's family and intended to intimidate other political activists.

Shang said Liu Xia's decision to pursue legal action was driven by her frustration over the way authorities have treated her family, and that her brother's conviction in particular made her feel like she could no longer be silent.

"Her biggest worry at the moment is her brother. She feels guilty for causing such huge trouble and negative influence to his family," Shang said in an interview at a teahouse. "She says would do anything to alleviate her brother's suffering."

The move marks the latest, extraordinary step taken by Liu Xia to protest the alleged persecution of her family. A week ago, her lawyers released an open letter she wrote to Chinese leader Xi Jinping to protest the prison term given to her brother.

Since her house arrest, under close watch by guards at her building and cut off from communicating with most of the outside world, Liu Xia has had few opportunities to express herself. She initially feared further retaliation if she chose to speak out.

Liu Xia was permitted a rare opportunity to leave her apartment briefly on Thursday and meet with her lawyers, handing them a letter authorizing them to prepare a legal petition that her husband's case be reopened, Shang said. She also gave them a separate letter entrusting them to represent her in suing the Beijing police for keeping her under house arrest since her husband won the Nobel prize in 2010.

Liu Xiaobo is serving an 11-year prison sentence on subversion charges brought after he co-authored a bold call for sweeping changes to Beijing's one-party communist political system. He was convicted in 2009 and a court dismissed his appeal in early 2010.

In 2010, the Nobel committee awarded the peace prize to Liu, infuriating the Chinese government, which denounced the award, called Liu Xiaobo a criminal and locked up his wife in her home.