But Ms Chidlow’s solicitor, Alan Roberts, argued she had used her own judgment, and administered the drug because the second patient was distressed, after waiting five hours for treatment.
He said she had checked the patient’s details, date of birth and prescription and had given the correct drug.
The Trust’s policy is to only give drugs to the person named on the outside of the packet.
Labelling mistakes must be reported to the pharmacy straight away – a step Ms Chidlow did not take.
A written report must also be completed as soon as possible.
However, this was delayed, because Ms Chidlow initially forgot.
Expert witnesses said this was understandable because she was recovering from post- natal depression, which affects the short-term memory.
Ms Chidlow did feel fit enough to return to work.
Mr Roberts said it was common practice after calling the pharmacy for nurses to be told to scratch off the wrong name and write on the new one, but the Trust denied this.
The tribunal’s judgment reads: "It seems to us that what the claimant did was gross misconduct."
"Firstly, she made a mistake and did that knowingly.
"She then compounded the mistake by not reporting that immediately, as she should have done.
"Procedures are put in place to protect patients."
Miss Chidlow and her solicitor say she will appeal against the decision.