Bella Hadid strutted her stuff through LAX, on Monday, like a supermodel on the runway ... oh yeah, she IS a supermodel and the sidewalk is always her catwalk!

The 19-year-old wore all-black, accessorized with a bright red purse as she made her way to her flight. She's getting TONS of work -- just like older sister Gigi is -- following in the footsteps of their mom Yolanda Foster, who's battling Lyme disease and going through a divorce from hubby David.

All-in-all, the holidays may have been a bit rough for this teen -- in addition to her family issues, she reportedly split from boyfriend The Weeknd. HOWEVER, some reports claim the split is only rumor and that the two are just busy and not able to see each other much BUT they're still together.

Meanwhile, Bella's keeping busy -- she recently starred in a video promoting her second LOVE magazine cover -- in the publication's annual advent calendar clip. Check it out ...