Mrs Frances Brooke (1724-1789)
From 18th Century Literary Anecdotes

Mrs. Brooke having repeatedly desired Johnson to look over her new play of 'The Siege of Sinope' before it was acted, he always found means to evade it; at last she pressed him so closely that he actually refused to do it, and told her that she herself, by carefully looking it over, would be able to see if there was anything amiss as well as he could.

'But, sir,' said she, 'I have no time. I have already so many irons in the fire.'
'Why then, Madam,' said he (quite out of patience), 'the best thing I can advise you to do is, to put your tragedy along with your irons.'

From Memoirs of the Life and Correspondence of Hannah More (1834), i. 200-201.