If you jump out of an airplane with a friend, you fall together. The interaction between you and your friend is the same as the astronaut with the space ship, or other objects. They can push them or pull them, but there is no force to hold them together. So it is very easy for an astronaut to push himself or an object away from the ship and lose it. To keep this from happening, astronauts use tethers.
Tethers are straps or cables that are used to tie things to the space ship.
She can't just walk. To walk on earth, you need gravity to hold you to the surface. Otherwise, you would just push yourself away from the planet with the first step. Astronauts use hand holds to pull themselves along. These are handles that are bolted to the space ship.