I can make her grab marine animals and ride them but I can't make her interact with the other objects in the game.

You have to be pretty close to, and be facing, the object you want to interact with, then just send out a "ping" pulse by hitting the spacebar (or 'square' key if you are using a controller) and that should do it.

Note however that you can only interact with a limited number of things in the environment at first (mainly artificial items like the little broken-robots , doors, pools, etc. ), and that some later objectives need to be "unlocked" by solving a puzzle first, before you can get them to respond.

Most of these puzzles involve simple manipulation of one or more items near the objective you are trying to unlock.