Depending on the light source this is very easily noticed on that range. People have successfully "flashed" the International Space Station from the ground using both searchlights and a laser pointer. Over a distance of several hundred kilometers if not thousands.
https://www.universetoday.com/93987/ama ... e-station/
There are some caveats, the space station must be in the right light conditions (otherwise reflections on the station windows makes it hard to see anything outside) it must be night where the light-source is located and of course someone needs to be looking.
In this case it's a much closer distance, and on top of visual cameras the station has a whole sensor array pointed at Niobe and is looking at it "intently" - I'm pretty sure a directed flash-light signal from a cockpit window would be noticed even with starlight in the background. Unless the angle is such that the sun (or whatever the star is called) is getting reflected from the hull (or directly behind the ship) overshining everything around it.
If you want to sneak up on a station, the best approach angle to stay unnoticed is probably the same as an aerial sneak attack: Come directly from the direction of the sun.