Mell's friends bought two bowls of ice cream, so that was a cost of 2 * 3 = $<<2*3=6>>6.
They all three bought two cups of coffee each, so they ordered 2 * 3 = <<2*3=6>>6 cups of coffee in total.
The cost of the coffee was therefore 6 * 4 = $<<6*4=24>>24.
All her friends bought one piece of cake each, so the cost of it in total was 3 * 7 = $<<3*7=21>>21.
Mell and her friends spent in total 6 + 24 + 21 = $<<6+24+21=51>>51 at the cafeteria.
#### 51