The 28 year old, who landed a small role in 2009 horror Drag Me To Hell, is accused of marrying American musician Kent Ross in 2005 so she could obtain permanent residency in the U.S.
During the trial, the jury at Los Angeles Federal Court heard how Romero reportedly began an affair with celebrity photographer Markus Klinko in 2007, despite being married to Kent, and told the snapper she only wed for immigration purposes.
Prosecutors claimed Romero and Kent never lived together and alleged the musician was paid $5,000 (£3,330) to tie the knot with the actress.
Both defendants pleaded not guilty to counts of marriage fraud and making false statements, but they will face a fresh court case next year (11) after jury members failed to reach a unanimous verdict.
Jurors sent U.S. District Judge Manuel Real a note on Thursday (02Sep10), insisting chances of reaching a clear decision were "nonexistent" because one juror was refusing to pay attention to the evidence.
Expressing his surprise at the jury's actions, Real states, "This is the first time in my years on the bench I've had this problem."
On Friday (03Sep10), the judge declared a mistrial and set a status conference for January (10).
But Romero's attorney, Michael Nasatir, is angry the case has been drawn out and insists his client has done nothing wrong.
He says, "We're very disappointed the jury couldn't reach a verdict. These are two of the nicest people I've ever met. They are not a danger to society and enough is enough."
Romero and Kent are facing up to five years behind bars if convicted of the charges.