Alliyah loves to be served, make no mistake about that. But what she really wants from her pets it to be adored. To have them literally worship the ground she walks on, and to adore her tirelessly. So after she has this pet fetch her some water and her phone, she then has him lick the bottoms of her shoes. It has to be the bottoms because that's what really shows her how much this slave worships her, that he is willing to lick the dirt of the shoes she walked around in all day. That's loyalty, that's service, that's what makes a proper adoring slave.