Suddenly when I text a message on my iPhone it shows up on my wife's new apple computer. I would like messages that are sent out on my iphone to only go to the number text message is being sent to.
This is built into Messages (the application) so any texts that you send over iMessage (in blue instead of green) will be shown on your computer.
To remove the iMessages account from the Messages application open Messages on the computer you would like to remove it from.
then disable the account or click the minus sign if it is available.