The 16-year-old X Factor hopeful has been romantically linked with the eliminated singer in recent weeks, and has confirmed that they are "close".
"Sam and I are close, we are a unit. We understand each other," she told The Sun.
"He wasn't getting the best comments from the judges but he does things in a positive way.
"He is a really good support system."
Foster recently played down reports that she was dating Sam Callahan, saying that she is not ready to embark on a relationship at the moment.
She has also revealed that she has become good friends with One Direction's Niall Horan.
Tamera Foster reached the final five of this year's X Factor on Sunday (November 24), along with Luke Friend, Rough Copy, Sam Bailey and Nicholas McDonald.
Watch Tamera Foster perform 'Impossible' on The X Factor below: