Syaoran and Sakura Li
...the original clones.....
She loves them, these two are probably Yuuko’s favorite; because for them she gives her life (she pays for Sakura to be reborn with the prices of all the wishes stored in the shop, while for Syaoran she uses the remaining magic of Clow - thus her life), makes her time to slowly flow till her end just so those two would get a real life and not be clones (and in CLAMP paradoxical way become real Syaoran's parents and by this extent Watanuki’s too).
She also is the one that protects the tube with those two in it; that decided to revert their own time just so they could protect their children - Tsubasa (real Syaoran) and Kimihiro. She created the shop - a world on it’s own to protect the tube so that the two clones wouldn’t have been found till the time was to come.
She breaks the tube on the verge of her own death releasing the two so they can go help, to protect whom is the most important to them; aside their own love for each other.