By Brenda Goh and Engen Tham SHANGHAI (Reuters) -Esther Zhao thought she was doing the right thing when she brought her 2-1/2-year-old daughter to a Shanghai hospital with a fever on March 26. Three days later, Zhao was begging health authorities not to separate them after she and the little girl both tested positive for COVID-19, saying her daughter was too young to be taken away to a quarantine centre for children. Doctors then threatened Zhao that her daughter would be left at the hospital, while she was sent to the centre, if she did not agree to transfer the girl to the Shanghai Public He…