And as I've said before, and shall doubtless say again, little Tuppence can look after herself, thank you!" And with a short, sharp nod of her head she walked briskly onward.
Tuppence admitted that she can't take care of herself, and committed suicide. 
mnli hypothesis: Tuppence admitted that she can't take care of herself, and committed suicide.  premise: And as I've said before, and shall doubtless say again, little Tuppence can look after herself, thank you!" And with a short, sharp nod of her head she walked briskly onward.