Female cockatiel whistling

Our 9 month old cockatiel fluffy singing and whistling away.... with her own made up tune.
She sings as and when she wants to when she's in a good mood (even at inappropriate times like 2am in the morning) but she is also prompted by us doing pinching motions. We trained only her to wolf whistle and have attempted to teach her jingle bells. Clearly the latter was a fail lol.
She loves demanding for scratches aka scritches. She's a lovely bird and we love her to bits. :)