。
She was saying she'd been happy.
Literal
She [topic-は] happy was [quotative-と] was-saying.
言っていました combines the polite past form of 言う ('say') with ~ている — 'was in the act of saying' / 'was saying.' This is a key contrast: with reporting verbs, ~ている often indicates a habitual or continuous state of utterance rather than a single instantaneous remark. 幸福だったと captures her past tense: she said 'I was happy.' The embedded clause's tense is preserved exactly — Japanese doesn't 'shift' tense in indirect speech the way English sometimes does.