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Did... She just set the speed of light to 1?
This isn't uncommon in lots of physics calculations where you are working at the same scales a lot and its cumbersome to keep carrying the constants around and it adds risk of making a mistake.
Think of it as assuming you are working in a system of units where you measure all your speeds relative to the speed of light. So rather than saying the speed limit of a road is 30mph you would say its .000000045c.
She's measuring distances in light-seconds. Then the speed of light is 1 light-second per second
1 what? Cucumber per nanosecond?
1 speed of light of course.
Light-second per second
Actually, yes. Light travels about 30cm in a nanosecond, around the size of a cucumber.
Which is why I updated my comment from "banana per nanosecond", which itself was originally updated from "apple per picosecond" that I just put there randomly, without any thought.
Is there another way to measure the speed of light?
It's just a number, and all units are relative. So if you set it to 1 and make sure the equation still is valid it doesn't matter.
It is matter, though.
Except at the speed of light?
What about plaid?
It’s ludicrous!
Just use the only practical unit of length, "lengthunit", which is equal to 299792458 meters (whatever those are...) times the only practical unit of time, "time unit", divided by a "second" (whatever that is...).
A "second" is the 2nd division of an hour.