。
She was wearing pumps.
Literal
She [topic-は] pumps [object-を] was-wearing.
パンプス is the Japanese fashion-loanword for women's slip-on dress shoes — what English calls 'pumps,' British English 'court shoes.' The word arrived through the fashion industry and is firmly established in Japanese, distinct from ハイヒール ('high heels') and フラットシューズ ('flats'). はく ('wear on the lower body') is the dedicated wearing-verb for shoes, pants, skirts, and socks; 着る covers tops and dresses, かぶる covers hats. The progressive はいていた describes the resulting state of being shod, not the act of putting on.