She definitely is well trained singer. Her song selection is bad. Also I think she looks too over confident which is not good for someone just starting out. I remember in one of the episodes Alka yagnik actually scolded her for over performing a song. If she is concentrating too much on her performance she will lose on singing. But she was rather rude saying that she wants to be aperformer too. That is fine, but singing is more important also. Also I think she has difficulties in high range and she can sing only few songs with huskiness required. CAnnot really say she has conventional bollywood voice, but might become successful with her charm.
also I feel her performance is not natural and appears made up. The naughtiness, sexiness in a song should come in the voice, not on the face.
Sunidhi Chauhan is successful because of that in her voice. But Twinkle is still young and may be will mature in all ways