After 2 years of singing lessons she still sings off key?

My daughter has been in lessons for 2 years. Although her voice is strong and beautiful, I believe she is tone deaf as she still frequently sings off key. Should she get another vocal coach? She works very hard and still seems tone deaf to me. Is she wasting her money on lessons? Is this something that can be... show more My daughter has been in lessons for 2 years. Although her voice is strong and beautiful, I believe she is tone deaf as she still frequently sings off key. Should she get another vocal coach? She works very hard and still seems tone deaf to me. Is she wasting her money on lessons? Is this something that can be overcome?
Update: She's 20.
Update 2: Her coach holds a doctorate in music, so I'm assuming he's qualified.
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