She was quite young, not more than eighteen.
( She ( ( ( was ( ( ( quite young ) , ) ( not more ) ) ) ( than eighteen ) ) . ) )
(ROOT (S (NP (PRP She)) (VP (VBD was) (ADJP (ADJP (RB quite) (JJ young)) (, ,) (ADJP (RB not) (JJR more))) (PP (IN than) (NP (NN eighteen)))) (. .)))
The girls was at least eighteen years old, but not much older. 
( ( The girls ) ( ( ( was ( at least ) ) ( ( ( ( ( eighteen years ) old ) , ) but ) ( not ( much older ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS girls)) (VP (VBD was) (ADVP (IN at) (JJS least)) (ADJP (ADJP (NP (CD eighteen) (NNS years)) (JJ old)) (, ,) (CC but) (ADJP (RB not) (RB much) (JJR older)))) (. .)))