Again, why does iHeart carry her show if the demos are as old as you say? Wouldn't they want a younger host attracting a younger demographic?
At some point, her contract will end, and they will move on. Until then, she's on at nights in a daypart that really isn't critical to ratings.
Having said that, the AC format trends older. About 30% of the audience is 55+. In the talk format, over 60% is over 55. Not every format aims at young people. The median age for talk is 60. Median age for AC is 45.