The daughter of Sen. Dianne Feinstein, D-Calif., has been given power of attorney over the sitting senator and is handling the 90-year-old's legal affairs,

Katherine Feinstein, 66, has filed two lawsuits on her mother's behalf in an effort to gain access to the estate of the senator's late husband. The senator's decision to delegate management of her affairs comes as Democrats and Republicans on Capitol Hill argue whether Feinstein is no longer fit for office.

Katherine's first lawsuit on her mother's behalf relates to a California beach house owned by the senator's late husband, Richard Blum. The lawsuit argues that Feinstein is seeking to sell the house in order to raise funds for her ongoing medical treatments.

The second lawsuit challenges the appointment of two other trustees in Blum's estate: Michael Klein, a longtime lawyer for Blum, and Marc Scholvinck, a business partner of Blum's, according to the New York Times.

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The lawsuit argues the pair have withheld Blum's life insurance proceeds from Feinstein, despite her claims that she needs the funds to pay for medical expenses, going on to note Blum's "intent to support his spouse after his death."

Klein and Schlovnick's attorney, Steven Braccini, has flatly rejected the claim, saying Blum's estate has never withheld any funds that Feinstein has requested.

"My clients are perplexed by this filing," Braccini told the Times. "Richard Blum’s trust has never denied any disbursement to Senator Feinstein, let alone for medical expenses."

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Feinstein's office did not immediately respond to a request for comment regarding her need for Katherine to manage her legal affairs.

Adam Russell, a spokesman for Feinstein, declined to comment in a statement to the Times, saying it "is a private legal matter. Senator Feinstein and her office won’t have any comment."

Feinstein's fitness for office has faced increased scrutiny in recent weeks as worrying incidents continue to mount. Last week, a hot mic caught the senator appearing confused during a routine Senate committee proceeding, where she began reading from her prepared remarks instead of saying "aye" during a roll call vote.

Fox News' Kyle Morris contributed to this report.