Why does my cat lick my face?

My cat LOVES to lick, but especially lick my face, like a dog!! she even drinks out of the toilet like a dog, AND will follow you around like a dog....my other cat, and cats i've had in the past, hardly ever lick me, but Izzy licks and licks and licks, especially at 2am when you're trying to sleep....she LOVES licking your face then.....I just wonder why she does this when Isis doesn't (Isis and Izzy!!)