"To the most selfless person I know," Khloe wrote on Instagram. "Mom, the words 'I love you' are not adequate enough to express how grateful I am to be your daughter, how much you are appreciated or how much you will always mean to me, so I will simply say: Thank you mom for being my superhero, my inspiration, my miss fix it, my problem solver, my expert-in-everything, and most importantly my very best friend."