Malin. It's uncommon, and pretty while still sounding mature enough to transition to adulthood.
I despise Kinley and Lexi is NMS at all. I don't even care for full versions like Alexandra, Alexa, etc...something about the X in there bugs me.
I like Malin Alexandra if you want to tie that in, but I think other middle names would sound better with Malin. Rose, Elise, Brielle, Violet, Paige, etc..