SOLVED. Could be YA not sure Mentally disturbed woman drowns her mother in eggs

[Georgia]

I'm not sure if this was a YA book or not because me sister read it sometime in the mid to late 1970s and I can't remember if she was still in high school when she read it. I thought it was called Almost Normal but can't find a book by that name that fits that description.
I seem to recall that a woman was hired to help take care of a mentally disturbed woman that was living with a mother that was critical of her. Or the mother was controlling. Something like that.
The mother was always telling her daughter that washing one's hair in eggs made it more beautiful or some such thing. So towards the end of the book or maybe it was the very end the daughter finally just drowns her mother in eggs.

[Becca]

The Girl Who Passed for Normal by Hugh Fleetwood looks like a match - you can search the Google Books preview for the word 'eggs' here - https://books.google.co.uk/books?redi...

[Kris]

Georgia, we notice you added "Solved" to the topic header. Is your book The Girl Who Passed for Normal by Hugh Fleetwood - Becca's suggestion?