She got a very flattering haircut
Larissa has always been a beautiful woman, which is probably why Colt wanted her as his sex-doll-slash-wife, but she got new makeup and a new haircut as part of her new lease on life.
It's not clear what else she did
Larissa has always had clear cheekbones, but it's POSSIBLE that she got fillers in her face. Others believe that she may have received lip fillers. We've seen a lot of over-the-top procedures on celebrity faces, but Larissa has gotten some very nuanced work done. Very subtle.
It was just what she needed
Not because she was lacking in beauty, but because she wanted a confidence boost
And it didn't hurt her brand, either
With months to go before 90 Day Fiance: Happily Ever After? returned, she needed to remain relevant for her fans and followers. It can't be all drama, all of the time -- that's exhausting. Fans want happy updates, too.
Plus, she was back on the market
Larissa joined Tinder and created a profile for herself, making it clear that she was looking for a new relationship, not just some convenient boning
Larissa had been so unhappy for so long
Colt insisted that Larissa be beautiful and sexy for him like some sort of fantasy housewife (embodied in a recent episode when Larissa was washing dishes at the sink while wearing a leather skirt), but didn't feel inclined to buy her makeup or dresses or jewelry to help her do that.