It is understood that Haq Nawaz was held by police in the Punjab city of Jhelum after an alleged attempt to prove she died of natural causes, the BBC reported.
The arrest comes after her father and first husband were remanded in custody till September 5 in connection with her death.
While her former husband, Chaudhry Muhammad Shakeel, is accused of murder and is reported to have confessed to strangling her with her scarf, Chaudhry Muhammad Shahid, her father, is being held as an accessory to her murder. according to local police.
Samia Shahid, 28, from Bradford, died in July in northern Punjab when she had been visiting family in the village of Pandori, and her relatives initially claimed she had suffered a heart attack.
In a second development, the policeman who initially headed the murder investigation has also been arrested.
Aqeel Abbas is being held for allegedly trying to conceal evidence relating to Shahid's death.
Her second husband, Syed Mukhtar Kazim, believes she was the victim of a so-called honour killing as her family did not approve of their marriage, the BBC added.
A post-mortem examination confirmed she died as a result of being strangled.
On Friday, police told the BBC they intended to proceed with a prosecution against both Shahid's father and first husband for her murder.
