Fetching details from the dictionary...
to abandon oneself to grief
悲報を聞いた彼女は泣沈んでしまった。
She sank into grief upon hearing the sad news.
泣沈む友人の肩にそっと手を置いた。
I gently placed my hand on my grief-stricken friend.
友の死を知って彼女は泣沈んだ。
She abandoned herself to grief upon learning of her friend's death.