Well, not exactly immediately, as she had to be convinced by several people sending her PMs. All Hannon had was a tweet she sent later on that day about deleting it because of "hate post". Not sure if she was referring to the people she "knew and respected ", or others.That's as I said, she took down the tweet and apologised immediately.
Hannon knew the tweet was deleted immediately, he may have not know she apologised but that doesn't give him the right to do a hatchet job on her 6 months later.
The fact she deleted it should have been closed.
But taking your point, all she had to do was mention this in the interview and that probably would have ended it quickly and moved onto something else.