I had to dig out my copy of the novelisation by James Kahn as I couldn't find anything online I may have been remembering it incorrectly as it refers to a trunk which could be a tree or a box :
"Leia...do you remember your mother? Your real mother?"
The question took her totally by surprise. She'd always felt so close to her adopted parents, it was as if they were her real parents. She almost never thought of her real mother-that was like a dream. Yet now Luke's question made her start. Flashes from her infancy assaulted her-distorted visions of running...a beautiful woman...hiding in a trunk. The fragments suddenly threatened to flood her with emotion.
"Yes", she said, pausing to regain her composure. "Just a little bit. She died when I was very young."
"What do you remember? he pressed. "Tell me."
And later...
She moved away from him, to deny his words; at least to give them distance, to let her breathe. Flashes of her mother came again, in this breathing space. Parting embraces, flesh torn from flesh...