Let's say I live in Toronto (an expensive city to live in) and make 10$/h after taxes working at Starbucks.
40h/week, 4.5 weeks/mo = 1800$
Bedroom in apartment = 700$
Metropass = 150$
Phone = 50$
Internet = 50$
Food = 350$
Total = 1300$
That's 500$ left for things like going out, clothes, etc.
Nobody is exploiting your friends - it sounds like she complained to you, you took her words at face value and concluded that those other people are at fault.