。
Mother takes a bath every other day.
Literal
Mother [topic-は] 1 day [interval-おきに] bath [in-に] enters.
おきに is the suffix for 'at intervals of' — 一日おき = 'every other day,' 一週間おき = 'every other week,' 一つおき = 'every other one.' The pattern [amount + おきに + verb] is the idiomatic way to say 'every other,' not the literal-sounding 二日に一度 or 毎他日. 風呂に入る ('enter the bath') is the standard idiom for taking a bath; に here marks the container entered.