Always on at me/she could not have heard what she thought

Hi

Miss Benson and Miss Mayfield are talking. Miss Benson tells Miss Mayfield what she should do to look better (lipsticks, powders).

Honestly, it’s only because you are such a dear, and it seems a pity you don’t make the best of

yourself. Ma Westleton, now, she could rub her face in Bath brick for all I’d care. Actually, she was always on at

me – where did I get my hair cut, what powder did I use. I used to give her a bum steer every time.’ I take it to mean that Mrs Westleton always criticized her, always criticized her haircuts, the powders she used and she gave her bum steers?

‘A what?’ asked MissMayfield, thinking that even in her present distracted state of mind she could not have heard

what she thought. Does Miss Mayfield asked "A what?" because she was distracted and didn't hear that word she used? Or maybe she was distracted and couldn't hear her own thoughts, so she stopped thinking and asked "A what?"

Sorry. It’s an American expression, meaning wrong direction, hint or advice. I got quite a kick out of seeing her

look sillier than usual. All for the Canon’s benefit, of course. But you, that’s different. . . .

There's something I do not get here. Miss Benson says she gave wrong advice to Mrs Westleton and she said before that Mrs Westleton criticized her. So if Mrs Westleton criticized her why did she want any advice from her, something's illogical here. Or maybe the part "where did I get my hair cut, what powder did I use" says that Mrs Westleton admired her haircut and the powders she used?