。
She pulled her head back from the window.
Literal
She [topic-は] window [from-から] head [object-を] pulled-back.
引っ込める is a compound verb 引く ('pull') + 込める ('put into') in a transitive form — 'pull back, retract, withdraw.' Used physically (引っ込める手 'pull back one's hand') and metaphorically (発言を引っ込める 'retract a statement'). ~から marks the source of motion — pulling back from where the head was sticking out. The image is of someone who had been peering out of a window now retreating inside.