。
She sometimes gets depressed.
Literal
She [topic-は] depression state [to-に] become [sometimes-ことがある].
憂鬱状態になることがある — ことがある in its habitual sense means 'it sometimes happens that.' 憂鬱状態 (ゆううつじょうたい, 'state of depression') is a formal medical/psychological compound.