Now, she's made the change completely-changing both her username and her bio to 'Hailey Bieber'.
There is no trace of "Baldwin" left, as Hailey opted to ditch the hyphenated trend that some women with memorable or powerful last names seem to follow.
However, the following day, Hailey denied she had married the 24-year-old popstar, tweeting: 'I understand where the speculation is coming from, but I'm not married yet'.
Her new name comes after she filed to trademark her married name last month.
Soon after the post, Baldwin changed her Instagram handle to her married name. They added that the "Sorry" singer was crying and at one point told Hailey, "I can't wait to marry you, baby".
In the candid photo, Hailey and Justin hold hands, showing off the massive rock on the model's finger.
"My wife is awesome", the singer captioned the photo, showing Hailey wearing baggy I AM GIA trousers, a white cropped t-shirt and a red baseball cap.
In September, months after announcing their engagement, rumors swirled that Bieber and Baldwin were married and were spotted at the New York City Marriage Bureau. The couple were reportedly married in a secret ceremony a few weeks ago and they have finally confessed that they are man and wife.
"He is incredible", Baldwin said of the pop star.