Discuss the reasons to why Watson doubted Laura lyons when he interrogated her the first time?

Laura changes and fabricates her story. Growing nervous then angry, she initially denies asking him to meet her but backtracks when Watson quotes the portion of the letter that Mrs. Barrymore had found. She swears that she never kept her appointment because of another circumstance she does not wish to discuss. When Watson threatens to involve the police, she confesses the contents of the letter: her husband was pressuring her to move back with him, and she was borrowing money from Sir Charles to ensure her freedom. She did not keep the appointment because she received the money from somewhere else.