When you go to a restaurant, do you expect the server to pick up your baby and take it for a walk while you eat your dinner? No.

When you go to the theater, do you expect the usher and door staff to walk your baby while you enjoy the performance? No.

My point here is that there is nothing different about air travel than these other experiences. The staff (in this case, the FAs) are there to ensure an enjoyable and safe experience for all passengers.

If your friend wanted an on-board nanny, she should have hired one.

I really don't understand people's ideas that somehow travel in an airplane should encompass all sorts of things that travel by train or bus doesn't. When all is said and done, it's the same thing. You can argue that this was business class and there should be better "service" and then twist the word "service" to imply that you should receive whatever benefits you want, but even the most luxury coaches on the Orient Express don't come with a built-in nanny, either, so the analogy stands.

I'm going to take it a step farther and hazard a guess that your friend didn't even buy her kid a ticket (other than the 10% infant fee, anyway), so I will repeat what I have said to many others: She chose to go the lap infant route, so she got her just deserts.