Gabbard was reacting to Trump's tweet on Sunday that the US was "waiting to hear from the Kingdom as to who they believe was the cause" of the attacks "and under what terms we would proceed!"
Gabbard, who is vying for the Democratic nomination in the 2020 presidential election, tweeted later: "Trump awaits instructions from his Saudi masters. Having our country act as Saudi Arabia's b---- is not 'America First.'"
Gabbard has attacked Trump's relationship with Saudi Arabia before, using a similar insult in November. Her policy platform includes ending the US's alliance with Saudi Arabia.
Gabbard's own Middle East policy has also been attacked, particularly her choice in 2017 to meet Syrian President Bashar Assad, a foe of Saudi Arabia who's been accused of war crimes.