I wouldn't risk the sickness, get a suitable medication for DD. You wouldn't want her first flight to be marred by feeling/being sick, plus will be doing a favour to all the other passengers. If you have a potette, have it set up with a liner, in the event of the tablet not working, just the fact that there is something to be sick in can act as a placebo. Don't try to manage with the paper sick bags.
You could prepare her by having a visit to the airport, to look at the planes taking off and landing, possibly look around the landside terminal. You can explain about the suitcases going on a ride on the conveyor to be loaded onto the plane, and how the pilot 'drives' the plane. Look for books for children about travelling on a plane.
Take spare clothes in hand luggage, and a favourite toy. Make sure DD has snacks and a drink (not fizzy), you could have a special trip to the airside shops to buy these.
On the plane, keep DD occupied so that she is less likely to feel poorly or anxious; read a story, draw, play with small toys, but with a history of motion sickness it's best not to play with computer style games. The flight itself shouldn't be very long, so this should be OK. Some new comics might be good, often they have little toys/novelties attached. The comics are handy to fold into your bag when disembarking, and get one out while waiting in boring security queues, or waiting for luggage, etc.
Most importantly, if you are calm and relaxed, DD will be.