The umbrella, when it rains - Evelyn, because if she doesn’t Theta will get distracted and move it and they’ll both end up wet
The popcorn at the cinema - Theta, she doesn’t get too into movies (mostly because she’s seen them already) so Eve makes her hold the popcorn so she won’t leave
The baby, when it cries - They both do. Theta’s had more practice though.
The ice cream cone, when they share - Share? What do you mean share? These two don’t share (But it would be Eve and she’d end up eating most of it)
The remote, when they sit down to watch a movie - Evelyn. Theta gets animated when she watches TV and Eve learned the hard way to not let the Time Lady have the remote
The basket, when they go shopping - Theta. Eve doesn’t trust her to not add things they don’t need
The door, on dates - Theta. After Nine regenerations as a guy she still pretty much assumes the role
The other’s hand, most often - It’s pretty equal. Eve takes Theta’s hand to prevent her from wandering, Theta takes Eve’s to stay close
Their breath, upon seeing the other on their wedding day - Theta
The camera, when they take pictures together - Theta, Eve is always snuggled into her side