According to Ruth, why did she not look like the other mothers?

Ruth tries to dismiss his question:

'I asked Mommy why she didn't look like the other mothers.'
' Because I'm not them,' she said.
' Who are you?' I asked.
' I'm your mother.'
' Then why don't you look like Rodney's mother, or Pete's mother?
How come you don't look like me...'
'I do look like you. I'm your mother. You ask too many questions.
Educate your mind. School is important..