SOLVE THE CASES IF YOU CAN

Officer/detective before starting the case I would like to ask you a question
If you had the ability to change something what would you change??

Case - 2- my wife's murder

Your friend George comes to you he complained that his wife was murdered today at noon  when
he was in office
You were having 3 suspects.
You knew his past very well
he had 2 girlfriends before the marriage
and now the 2nd one was his best friend
you first go to the house for investigation
You find 2 cups of coffee one with red lipstick
you go to George and ask him about the red lipstick
he answers that before he went to office he drank coffee
with his wife
you leave him and you go to the first girlfriend
you ask her where was she while the murder
she answers that she was in the party whole day with her friends
and she said that she didn't like George's wife
when ever she sees George's wife she wanted to kill her
then you go to the 2nd girl and ask her where she was during the murder
she answers that she was in George's house killing her wife with poison
you was shocked by the answer
then you find a diary in her table
it was written in the cover MY DIARY, MY SECRETS
You slowly took the diary
you went to your house and read it
you found so many things written

and at last you find today's writing

there was written

Today at noon I felt really good when George came to me
and he proposed me for wedding.
I hated George's wife when she came closer
to him, I felt really good when they fought to each other

by reading this you went to the 2nd girl and you again ask her
who killed George's wife
she again blamed herself

Who is the killer officer?? And how did the killer killed the victim??
Find out and write the answer in comments

Don't forget to vote before continuing