The Joker Raises a Child, It's Fine, Really
Megan Damon is an autistic child personally picked up and raised by the Joker.
When she was little, due to her illness, she ignored everyone. When she grew a bit older, she asked the Joker, "Dad, Jonathan said you hit me when I was little."
Joker: ? Is Scarecrow just spouting nonsense and spreading rumors in Arkham?
"Dad, a strange man said he wants Robin and me to be his children."
"Dad, will you dress up as the Joker to pick me up on Halloween?"
"Dad, you're tricking children."
...
To the Joker, Megan was led astray when she was young, learning from Robin to "punch her daddy". Later, she became rebellious and disobedient, eager to do things he explicitly forbade.
This included, but was not limited to, reporting the Joker's prison breaks and bomb plantings to Batman, sabotaging his parties and plans, running away from home to play with her friends and staying out all night...
[This is all Robin and Batman's fault.]
(So your beloved daughter isn't at fault at all?)