An Argentina woman’s mother believes her daughter is mentally unstable for wanting to marry the man convicted of killing her twin sister.

In 2010, prosecutors believe Victor Cingolani killing model Johana Casas, 22, and leaving her body in a field. He was convicted of her murder and sentenced to 13 years in jail.

Cingolani had dated Johana but the two were reportedly not involved in a relationship at the time of her death. Instead, he claims Edith Casas, Johana’s twin sister is the true love of his life.

Now, as Edith prepares to marry her sister’s killer, her mother has submitted a request for a court-ordered psychiatric evaluation, postponing the wedding that was scheduled to occur on Saturday, December 22.

Other members of the family have stated they feel “a terrible betrayal” has occurred on the part of Edith.

Edith says that though Cingolani has been convicted of her sister’s murder he “would not hurt a fly.” Cingolani’s attorney claims a man named Marcos Diaz is Johana’s real killer.