Original Gretl Von Trapp disappointed by Carrie Underwood's Sound of Music performance

One of the original child stars of movie classic The Sound Of Music was left "mystified and disappointed" by Carrie Underwood's performance in a live TV production of the hit musical following its broadcast on Thursday night (05Dec13).

The country star portrayed Maria, the role made famous by Dame Julie Andrews in the 1965 film, for the special show, and although her stage turn won high praise from her music peers Kelly Clarkson, Miranda Lambert and Brad Paisley, reviewers were not impressed by Underwood's acting, blaming her lack of experience for letting the production down.

Marc Bernardin of The Hollywood Reporter wrote, "Underwood can deliver the songs...(but) she doesn't acquit herself so well when it comes to the carrying the emotional weight of the production... Underwood nails the look of a virginal almost-nun, but goes no deeper than that. Blank stares and placid smiles."

And it appears actress Kym Karath, who played youngest daughter Gretl Von Trapp, shares the critics' opinion.

She reunited with her movie sisters Charmian Carr, who portrayed Liesl Von Trapp, and Angela Cartwright, who played Brigitta Von Trapp, on Thursday to tune in to The Sound of Music Live!, but her excitement quickly disappeared as the TV musical unfolded.

Taking to her Twitter.com page, Karath wrote, "Mystified & disappointed so far by SOM (Sound of Music) special... Must admit some scenes are actually painful to watch... Love Carrie Underwood but this role is just not right for her. She is lovely her voice is beautiful but acting is wrong."

However, Karath wasn't appalled by all of the performances, reserving warm words for True Blood star Stephen Moyer, who played Captain Von Trapp.

Despite the mixed reviews, the three-hour special on the NBC network proved popular with viewers, attracting 18.5 million people, making it the most-watched program of the night.