I'm sure that what she calls herself is probably a stewardess, actually, but if that's her preferred term, I'm betting that she retired a long time ago. It's been 20 years at least since the terminology was changed to Flight Attendant.
I'm not going to say that you HAVE to use a carseat, because it isn't required by law, but I think you should make your decision on the basis of current information. The fact is that it *is* safer to use a flight-approved carseat, especially for a younger child who might otherwise be carried as a lap-baby. The FAA has tested it many times in turbulent conditions, and has recommended the use of carseats for kids under 40 lbs. since the mid-1980's. The safety margin is not as great as it would be in a private automobile, but there is a difference. Furthermore, it is a familiar place where the child knows that he/she must stay put, so it tends to help immensely with the squirmies, which your child is in the prime age range for. Seat-kicking can be a problem, but if you use a blanket to wrap down the child's legs, she won't be able to kick, and thanks to the higher position, she WILL be able to see out the window. (Where the seat will have to be; next to the window and not in the row directly in front of or behind the exit row.)
The Cosco Scenera (formerly called the Touriva) is a good lightweight seat that usually runs right around $40 at
Walmart, Target, etc. It has a 5-pt harness and can convert to a high-back booster when the child is tall enough.
It also fits pretty well in most rental cars, as it has a small base. We bought them as "Grandma's car" seats and borrowed them back when we went on trips. (The plus factor to that is not having to remove the one in your own car.)