Answer:
Gabriella is not moving
Step-by-step explanation:
This type of problem can be solved by having the concept of relative velocities clear. Two bodies move at Equal velocity 4 [m/s] towards Pierre. But they ask us about how Michelle sees Gabriella moving.
Since Gabriela moves at the same speed as Michelle, when Gabriela turns her head to see Michelle, she doesn't seem to move faster or slower than she does.
A classic example is when we are passengers of a car and in a window next door we see, a car next to us, this car seems static before our eyes, but we are aware that it moves at a speed equal to that of the vehicle we occupy.