They even smiled at Susan and she smiled back.
( ( ( ( They ( even ( smiled ( at Susan ) ) ) ) and ) ( she ( smiled back ) ) ) . )
(ROOT (S (S (NP (PRP They)) (ADVP (RB even)) (VP (VBD smiled) (PP (IN at) (NP (NNP Susan))))) (CC and) (S (NP (PRP she)) (VP (VBD smiled) (ADVP (RB back)))) (. .)))
They smiled at Susan, who in turn smiled back at them.
( They ( ( smiled ( at ( ( Susan , ) ( who ( ( in turn ) ( ( smiled back ) ( at them ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBD smiled) (PP (IN at) (NP (NP (NNP Susan)) (, ,) (SBAR (WHNP (WP who)) (S (PP (IN in) (NP (NN turn))) (VP (VBD smiled) (ADVP (RB back)) (PP (IN at) (NP (PRP them))))))))) (. .)))