。
She is taking care of her elderly mother.
Literal
She [topic-は] [aged-年老いた] mother's care [object-を] is-doing.
年老いる ('grow old, age') is a literary, slightly formal verb for aging — its past participle 年老いた modifies a noun as 'aged.' 世話をする ('take care of') is a stock phrase pairing with の (~の世話をする, 'take care of [someone]').