Was Mrs Croft really an invalid?

Question

In Agatha Christie's detective story Peril at End House, was Mrs Croft really an invalid? Or did she just pretend to be one?

We find out in the ending of the novel that Mrs Croft was a criminal. She could get away with pretending, because she came recently from Australia, so nobody really knew her past history. Pretending to be an invalid could give her an easy alibi, and indeed that method was used in at least one other Christie story. However, the ending doesn't seem to reveal whether this was the case.

Answer 1

Yes, Mrs Croft was really an invalid, and was not pretending. Chapter 19:

‘Hello-ello-ello,’ [Japp] said. ‘What’s this? An old friend! Milly Merton, I declare! And at your old tricks again, my dear.’

He turned round in an explanatory way to the company, disregarding Mrs Croft’s shrill protests.

‘Cleverest forger we’ve ever had, Milly Merton. We knew there had been an accident to the car they made their last getaway in. But there! Even an injury to the spine wouldn’t keep Milly from her tricks. She’s an artist, she is!’

(Blink and you’ll miss it!)