。
She was carrying a basket full of flowers.
Literal
She [topic-は] flowers [subject-が] full entered basket [object-を] hung-was.
花がいっぱい入った is a relative clause sitting in front of かご ('basket') — literally '(a basket) into which flowers have entered fully,' i.e. 'a basket full of flowers.' Note that inside the relative clause the subject 花 is marked with が (which can also alternate to の inside such clauses). 提げる ('to carry hanging from one's hand or shoulder') is a specific carrying verb — distinct from 持つ ('hold') or 運ぶ ('transport'). It's the verb you reach for when picturing someone with a basket, bag, or briefcase swinging at their side.