The House Democrat said shortly before the freeze expired at midnight Saturday that seven million people would be “at risk for evictions” over unpaid rent.
The freeze was imposed 11 months ago in part to halt the spread of infections through crowding in shelters.
Ms Bush, who was once homeless, wants the measure to be extended.
In a tweet early on Saturday, she wrote: “Good morning. The eviction moratorium expires tonight at midnight. We could have extended it yesterday, but some Democrats went on vacation instead.
“We slept at the Capitol last night to ask them to come back and do their jobs. Today’s their last chance. We’re still here.”
The Democrat-majority House of Representatives adjourned for a seven-week recess on Friday without renewing the moratorium.
Extension opponents say many landlords are struggling with their mortgage repayments without regular rent money.
Ms Bush, 45, said that despite managing only an hour of sleep in a chair, she was now preparing to spend another night outside the Capitol in Washington DC.
On Saturday, Democratic Senator Elizabeth Warren and Jim McGovern, a House Republican, briefly joined Ms Bush to voice their full support for her action.