She gave in to temptation and bought the jewelry.

Literal

She [topic-は] temptation [to-に] losing that jewelry [object-を] ended-up-buying.

誘惑に負けて is a set expression — 負ける ('to lose') takes に for what one loses to. ~てしまった marks the purchase as regrettable. 宝石 (ほうせき, 'jewel/jewelry') is the impulsive buy.