Dr. Strange was heavily involved in finding a way to cure Ava’s disease while allowing her to keep her phasing powers. Strange, keep in mind, is both a wizard and a surgeon. (Note: I read a fanfic where Strange and Bruce Banner cured Ava, so having Strange involved is NOT my idea) 

Due to somewhat of an age difference (Bucky technically being 100 if nothing else), Bucky calls Ava “kid,” a la “Casablanca.” When she phases, he says “Here’s lookin’ through you kid!” 

When Bucky’s arm gets a loose wire after a fight, Ava can stick her hand right into his and fix it 

When Bucky and Ava need science help of the sort that neither Bruce nor Strange specializes in, and Shuri is unavailable, they fret and argue, because Ava doesn’t want to ask Dr. Pym for help after trying to murder his wife, and Bucky doens’t want to ask Tony after killing his parents and leaving him in Siberia. 

Ava helped save everyone trapped in the Soul Stone, because she could phase through different universes (good god would I be happy if this turned out to be canon!) 

She has a problem with sleep-phasing though. She frequently falls through the bed and wakes up on or in the floor, in a wall, in the sky, in the refrigerator, and so on. It’s starting to get stressful.