She blew on her hands to warm them up.

Literal

She [topic-は] both-hands [object-を] warm [purpose-ために] breath [object-を] blew.

~ために marks the purpose — 'in order to warm.' 息を吹きかける (いきをふきかける) means 'to blow breath onto.' 両手 (りょうて, 'both hands') uses the 両~ prefix. A vivid everyday action.