Conservative commentator Ann Coulter lashed out at Sen. Marco Rubio, R-Fla., on Friday over his support of the GOP's tax plan, lamenting the impact of the bill's child tax credit on unmarried people who "will die alone."

"We singles live empty lives of quiet desperation and will die alone. Now Rubio is demanding that we also fund happy families with children who fill their days with joy," Coulter wrote on Twitter.

Earlier, Rubio and colleague Sen. Mike Lee, R-Utah, introduced an amendment to the Republican tax proposal that would incorporate a more generous child tax credit.

“Increasing the refundability of the Child Tax Credit from 55% to 70% is a solid step toward broader reforms which are both Pro-Growth and Pro-Worker,” Rubio, who had previously threatened to vote against the tax reform measures, tweeted Thursday.

With the backing of Rubio, Lee and Sen. Bob Corker, R-Tenn., the tax overhaul package is likely to pass the Senate when it returns to the upper chamber's floor.