。
She had a string of misfortunes last year.
Literal
She [topic-は] last-year unfortunate-things [subject-が] piled-up.
A characteristic Japanese double-subject construction: 彼女は marks her as the topic ('about her'), while 不幸なことが is the actual grammatical subject of 重なる ('pile up, overlap'). 重なる is intransitive — the misfortunes accumulate of their own accord, with no agent making them happen. Where English would say 'she had bad luck,' Japanese topicalizes the person and lets the events do the verb-work, framing her as the locus rather than the victim. This 'things happen of themselves' framing runs deep in the language; ~なる-style intransitives carry a lot of it.