。
She was satisfied with her new clothes.
Literal
She [topic-は] her own new clothes [with-に] was-satisfied.
満足する takes its object with に — 'satisfied WITH X' rather than 'satisfied X.' The past progressive 満足していた frames an ongoing state of satisfaction in the past — perhaps the speaker is recalling an episode where she was wearing or admiring the new clothes. 服 covers all clothing in modern usage; the modifier 新しい ('new') sits directly before it as an i-adjective in attributive form.