After being near an ally for 3 seconds that ally is marked (visible to Yuumi only), and she can attach to them. Upon attaching all shields on Yuumi get transferred to her ally (up to a cap), while attached Yuumi can cast all skills (movement skills will detach) and takes 40% of damage that's done to the allies health.

Her Q missile should lean into the mouse instead of following the mouse, and get increased projectile speed based on Yuumi's movement speed at the time of launch.

Her E temporarily increases her own movement speed as well as her hosts, and consumes a % of shielding to heal the host ( + base heal value).

Her ultimate should stay the same.

Hitting an enemy with her Q will reveal them and give % increased damage to her hosts next attack on the champion based on Yuumi's AP.

Her passive should stay the same but scale the shield she gets from it better, and more damage = more shield. (So that it works with her W.)