ABILENE, Texas -

HLN host Nancy Grace told Billie Dunn some people investigating the case are saying she is not a credible witness.

Hailey Dunn's mother, Billie Dunn, appeared again Monday night on the "Nancy Grace" show on the HLN network.

Grace continued to grill the mom about her statement last week that she was told she failed a polygraph test.

When we looked into that allegation last week, investigators told KTXS News neither the mother nor the boyfriend were informed about the results of their polygraph tests.

Monday night, Grace told Billie Dunn some people investigating the case are saying she is not a credible witness.

Dunn responded to Grace by saying she is not a liar.