Please help me identify this poem - possibly Milne?

Recently I remembered, for some odd reason, a poem which I was made to read and recite in fourth grade. All I could remember was the first two lines, and I’m not even sure if I remember them correctly:

“Wearing a little false beard of ill-will
and a toxic grin
She rides the broomstick
of her mother’s addiction”

(or condition maybe?) It was pronounced in three syllables (ad-dic-shin) to stay even with “toxic grin.”

The overall poem was about a little girl who dresses up as a witch and has some kind of emotional or psychological problem. I think it may have been by A.A. Milne. Could someone please help?

Definitely not Milne, unless he went through a hitherto unknown “Beat” period, and Google yields nothing. Sorry.