Pygmalion, Act 3

Eliza proved that she hasn't been completely transformed in terms of conversation..... she doesn't know what to talk about. Because of this, Higgins limits her subjects of conversation to the weather and health.

I've taught her to speak properly; and she has strict orders as to her behavior. She's to keep to two subjects: the weather and everybody's health--Fine day and How do you do, you know--and not to let herself go on things in general. That will be safe.