In a series of recently resurfaced tweets from 2011-2012, Baldwin -- who's now engaged to Bieber after just weeks of dating -- wrote gushing messages about the then-couple.
"I don't care what anyone says but Justin Bieber and Selena Gomez together is the definition of a teenage dream! #word," Baldwin, 21, tweeted in September 2011 -- and has since deleted -- according to The Cut.
In January 2012 Baldwin was at it again, Refinery 29 reports. The model called Bieber, 24, and Gomez "the perfect couple" in response to a since-deleted tweet from another user.
The next month, according to Brides, Baldwin expressed disappointment that the then couple didn't attend the Vanity Fair Oscars party together.
Baldwin and Bieber made it official when the "Sorry" singer popped the question in the Bahamas over the weekend.
"Justin decided to propose to Hailey in front of a group of people in the Bahamas, but had been planning to ask her for a couple weeks now," a source told ET following the engagement. "The ring is gorgeous and Hailey is over the moon with joy. The two can’t stop telling their friends and family how excited they are for their journey together. The two have always had a great bond, and it is stronger now than ever."
The engaged pair dated briefly in 2015 before calling it quits in 2016. A source told ET late last month that the pair have been "casually dating for roughly a month" and that "things seem to be heating up as the two are spending more and more time together."
Watch the video for more on their relationship timeline: