Hi, Ane4ka, and welcome to the G.E,
When turning the sentence "They say she has been ill" into the passive pattern, is it possible to say "She is said to be ill"? Or "She is said to have been ill" is the only correct sentence?
I see that the perfect infinitive works much better as it mainly replaces either the present perfect or the past simple in the impersonal passive structure.
1. 'She is said to be ill' refers to a present state and is the same as 'they say she is ill'.
2. 'She is said to have been ill' refers to the fact that she has been ill for a period of time and it is the same as 'they say she has been ill for ....'.