I think there will always be “writers” on Medium (and elsewhere) who will try to game the system. “You clap for me and I’ll clap for you” seems like just another way to try to do that. I think Medium can tell when someone claps but doesn’t spend long enough to actually read a story, and compensates for that. Your Facebook “friend” may think she’s doing everyone a favor by clapping for everyone’s story without reading them, but she is probably isn’t.
The simple fact is, if you claps for a large number of stories, your claps are almost worthless. If my understanding is correct, your $5.00 monthly fee (less if you pay yearly) is divided by the stories you clap for (minus any money Medium keeps?) Divide $5.00 by the number of claps you give per month and you will see that it often doesn’t add up to much.
In your friend’s case: 140 stories X 50 claps = 7000 claps. Divide $5.00 by 7000 = .00071429. Less than a penny per clap. Times 50 claps per story = 0.035. Three and 1/2 cents per story. And that was just one day. Clap more days and your claps keep going down in value.
It is a real irony that the more you read and clap, the less your claps are worth.