As an Astronaut goes out into space, her mass REMAINS THE SAME and her weight DECREASES.
When one travels away from the earth surface, one's mass remains the same but the weight decreases as the gravitation pull decreases.
The experience of weight on earth is as a result of the counteracting forces acting one's body and the ground. When one is in the space, this counteracting force is removed because the ground is no longer pushing back on one's body. Thus, one's weight will decrease in space because gravitational pull is lower above the earth's surface.