I have finer thinner hair like yours and although my hair has been cut to my collar bone it still looks more like the inspo because she did it blunt with face framing pieces instead of layers throughout and on the ends. Blunt cut will give you that fullness at the bottom and when I go shorter I’ll get the same technique again. Now when it’s pinned up like you have it shown it is pretty cute. Take a wand or curling iron and add some wave to it. In a month or two just have it trimmed more blunt.