TMZ's sources tell us ... the 24-year-old singer hit it off with the 31-year-old former UFC middleweight champ earlier this year while training at Unbreakable gym in Los Angeles.
Long story short ... we're told the two clicked right away -- and have even sent some secret inside messages to each other on social media ... including a back and forth with smiley face art on their fingers.
Congrats!
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