Yes, of course Liz Rosenberg denied it.
And really, who the hell cares? She shouldn't have done it. Move on. We don't even know she asked to go backstage. She's reportedly done this many times. (The tabloids blew up at her texting during "12 Years a Slave'; people reported she texted during FELA and at Rosie's TABOO; she even posted a picture of NPH in Hedwig during the Finale, obviously taken by her phone.)
But attacking her singing, her acting, her career, her age - really? I find it so amusing when these boards blow up with indignation and proudly declare a moral high ground over huge celebrities and the like. This may be a big story for Broadway, but for Madonna, it was a day that ended in 'day'.