She has believed that the sleeping draught she administered was perfectly harmless, but there is no doubt that for one terrible moment she must have feared that Mrs. Inglethorp's death lay at her door. 
( ( ( ( ( She ( has ( believed ( that ( ( ( the ( sleeping draught ) ) ( she administered ) ) ( was ( perfectly harmless ) ) ) ) ) ) ) , ) but ) ( there ( is ( no ( doubt ( that ( ( for ( one ( terrible moment ) ) ) ( she ( must ( have ( feared ( that ( ( ( Mrs. ( Inglethorp 's ) ) death ) ( lay ( at ( her door ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (PRP She)) (VP (VBZ has) (VP (VBN believed) (SBAR (IN that) (S (NP (NP (DT the) (VBG sleeping) (NN draught)) (SBAR (S (NP (PRP she)) (VP (VBN administered))))) (VP (VBD was) (ADJP (RB perfectly) (JJ harmless)))))))) (, ,) (CC but) (S (NP (EX there)) (VP (VBZ is) (ADVP (DT no) (NN doubt) (SBAR (IN that) (S (PP (IN for) (NP (CD one) (JJ terrible) (NN moment))) (NP (PRP she)) (VP (MD must) (VP (VB have) (VP (VBN feared) (SBAR (IN that) (S (NP (NP (NNP Mrs.) (NNP Inglethorp) (POS 's)) (NN death)) (VP (VBD lay) (PP (IN at) (NP (PRP$ her) (NN door)))))))))))))) (. .)))
The sleeping draught was not harmless, as it gave her violent diarrhoea.
( ( The ( sleeping draught ) ) ( ( ( ( ( was not ) harmless ) , ) ( as ( it ( gave ( her ( violent diarrhoea ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (VBG sleeping) (NN draught)) (VP (VBD was) (RB not) (ADJP (JJ harmless)) (, ,) (SBAR (IN as) (S (NP (PRP it)) (VP (VBD gave) (NP (PRP$ her) (JJ violent) (NN diarrhoea)))))) (. .)))