I have a bun, name's Smokey, who would do same things, she was very greedy on pellets and it is not good if she eats as much pellets as she can get, I wouldn't use automatic feeder for her. I have another bun who eats only when he is hungry and you can fill his bowl with 3 day portion and be sure on day 3 he still have them, but not with Smokey, she'd eat them all at once and would get a blockage. Same with water, she just messes it up and she is nt Flemish but she's big ad very strong when she had a water bowl attached to the wall she can't move it but she manages to mess it with hay so it is all dirty after a few minutes. Thankfully she drinks from a bottle very well, also if your bun has problems with drinking from bottle you can teach her, to get water they have to lick the ball, and it is important that your bottle is full and in strictly vertical position firmly fixed so she has no problem with it and ball don't get stuck. You can use giant size bottle it has much wider tube and larger ball and so much easier to use. I train my rabbits to drink from bottles, most of them would learn very quickly, but some would need more time to get it, they are trying to break the bottle or pull out tube but they only need to lick the ball and they will get it eventually.
With pellets, I had one day portion split into halves and gave half in the morning and half in the evening. As above you can also sprinkle them on hay so you won't need feeder at all. That would make her to eat slower.
Smokey is nearly 2 year old now and I can tell you she changed after she was one year old. She stopped growing by then and she's a bit calmer. She likes her food bowl which is attached to wall as a few comments above, but her bowl is metal. I don't fill it full she's not growing and she gets about 25-30 gram pellets daily which is a half of a standard daily portion for my other rabbits who are in their first year. Most of them are getting their portions cut after they are one year old since they don't need that much and they eat more hay and have enough energy for everything.
I feed her once a day now in the evening she has about 1/4 of her bowl, which is quite small size itself.
So I wouldn't use automatic feeder for her, give her pellets twice a day half and half daily portions, sprinkle on hay so she'd need time to find them, she will also eat some hay to get there.