。
The news gave her strength.
Literal
She [topic-は] that news [from-に] strength [object-を] gained.
力を得る ('gain strength, take heart, be encouraged') uses 得る ('obtain') to describe the acquisition of an abstract resource — energy, courage, or motivation derived from an external source. に marks the source: the news was what gave her strength. The phrasing has a slightly literary feel; more conversational alternatives include 元気が出る ('regain energy') or 励まされる ('be encouraged'). 得る in this idiom is the formal counterpart to もらう, suited to abstract acquisitions.