Anna Kepner's Mom Questions Why Daughter Was Sharing Room With Stepbrother

The mother of Anna Kepner -- the 18-year-old who was murdered on a Carnival Cruise ship -- is questioning the sleeping arrangements her daughter was placed in leading up to her tragic death.

Heather Wright told Fox News she's been villainized in the situation, but it's Anna's dad, Christopher Kepner, who could be partly to blame.

Anna was reportedly sharing a cabin with two other teenagers -- one of whom is her stepbrother, who's now suspected in her death. Anna's grandmother told ABC News the teenagers chose the arrangement themselves ... but Anna's biological mom seems to think an adult should have vetoed it.

She said, "Why am I the bad guy? He put them in the same room together."

Remember ... Anna's body was discovered tucked under a bed in the cabin she was sharing with her stepbrother. Her death certificate, obtained by ABC News, said Anna died as a result of "mechanical asphyxia" on November 6, and it noted the 18-year-old "was mechanically asphyxiated by other person(s)."

FBI agents found two bruises on the side of Anna's neck, and she's believed to have died from a "bar hold" -- an arm placed across the neck.

Wright separated from Christopher when Anna was just a child, and she had reportedly been estranged from Anna for several years. Wright claims Christopher further strained their relationship by banning her from attending Anna's memorial service -- so she had to go in secret.

Wright revealed, “They said I never went, but I did. I didn’t want to be seen, so I made sure no one seen me -- plus they can’t stop me from going anyway, even though Chris said he would have me arrested for back child support.”

Wright added ... "She was my daughter, and I loved her with all of my heart and soul.”