But, it would appear that she (though not Abbott) has in an interview denied emphatically an affair with Abbott.
But, to be forensic about it, only her answer appears*, not the question, and she does use the line:
The idea that my relationship with the prime minister was anything other than professional is completely falsewhich leaves open the possibility that her comment is limited to the time he was PM.
Thus I'm not giving up on my theory - that there is something further back that has prevented them from outright complaining about the affair rumour and innuendo (or threatening defamation) until now. (Though, granted, the way Savva has dealt with it does not leave open a defamation action against her.)
* I actually brought a hard copy of the Australian to confirm - sorry to have spent money on Rupert.
Update: and, by the way, I am aware of another rumour involving Abbott that does not involve Credlin. Mind you, nearly all politicians are subject to such rumour, but with Abbott's behaviour and famously "blokey" demeanour I make special dispensation for him for believing there is fire behind the smoke.
Update 2: Michelle Grattan's take on the whole matter is really quite harsh (on Abbott/Credlin), but fair.
Update 3: Credlin's actual opinion piece in The Australian today (which doesn't contain the express denial) is really awful - it actually is so close in parts to what Abbott said yesterday that you have to wonder whether she wrote his response for him!