Mariah Hamilton, the ex-girlfriend of rapper YNW Melly, has been arrested in Miami-Dade County on a warrant related to the rapper’s first murder trial. Hamilton, 24, was taken into custody on Sunday, with the warrant appearing to stem from Broward County. Allegations against Hamilton include failing to appear at Melly’s previous trial and witness tampering. Details of her arrest surfaced following her return to the U.S., according to Local 10 News…