Off course Shirley Collins can sing. She sings like Shirley Collins!   She sings in a totally honest, straightforward style, without histrionics or over elaboration, in her own Sussex accent, which adds to the charm of her singing in my opinion, No one can fault her for integrity,she has upheld her belief and love for traditional song for many years and continues to do so. Long may she reign. However, as she is a noted public figure, heard by many, there are bound to be some who do not like her singing. It's inevitable. Lots of people don't like my singing, but I'm grateful for those that do, and accept that the others have a right to their opinion. I love to sing, and will continue to do so regardless of having some critics. I'm sure that Shirley wishes she could sing right now. I too have suffered from Vocal Dysphonia, it was the darkest period in my life when I feared I would never sing again. It took me three years plus before I could use my voice with confidence once more.
Like Shirley's singing if you wish. Dislike it if you wish. It's just your opoinion after all. But to say that she CAN'T sing. Nonsense!