[Grammar] Indirect Narration : what about time factor?

[PENDSE]

Direct Narration :
She said to me, " I was teaching this lesson on his request."
Indirect Narration :
She told me that she had been teaching that lesson on his request.

Conversion is ok but what about the time factor which is said to be compulsory in a sentence pertaining to perfect continuous tense ?

If I try to add a time factor with since or for, it would be a false statement because the time factor has not been mentioned in the original sentence.

 

[bhaisahab]

Direct Narration :
She said to me, " I was teaching this lesson at his request."
Indirect Narration :
She told me that she had been teaching that lesson on his request.

Conversion is OK but what about the time factor which is said to be compulsory in a sentence pertaining to perfect continuous tense ?

If I try to add a time factor with since or for, it would be a false statement because the time factor has not been mentioned in the original sentence.

She told me that she had been teaching that lesson at his request. This is fine, you don't need any time reference.