McGowan sat down with KAMC News to tell her sister's story in hopes that the same thing wouldn't happen to her.
Her sister, 25-year-old Kechi Diaz, was found dead in her boyfriend's house in Lockney early Saturday morning.
"Everybody's just falling apart, nobody can handle it right now," McGowan said of her family.
Police were called to 508 S. 6th St. in Lockney by Diaz's boyfriend, 50-year-old Edward Hernandez, who, police say, confessed to killing her.
McGowan said she was with her sister when Hernandez picker her up in Lubbock Friday night. According to McGowan, the couple were fighting because Diaz wanted to leave Hernandez and go back to her ex-husband.
"When I find out my sister's been murdered by this son of a b***h who says he loved her then, you know, I couldn't believe it," McGowan said. "My first reaction was this is all a lie, its a nightmare I can wake up from but it hasn't happened."
Diaz had four children--three girls and a boy--with ages ranging from 9 to 5 years old.
"She was a great mom, loved her kids," McGowan said. "I have kids and she-- all of our kids were each others kids, you know, she was always about the kids."