Chickens eating rabbit food is pretty OK. Mine do it all the time because they are under the rabbit hutch. Chickens aren't very sensitive to what they eat, being opportunistic omnivores. Rabbits eating chicken food can be very, very bad because of their sensitive tummy that is designed to digest only one thing really well; grasses. Chicken feed normally has too high protein (rabbit feeds top out at 18%, typically being 15%, chicken feeds can be VERY high in comparison), and WAY too high calcium (rabbits are sensitive to calcium and should have less than 2% calcium in their diet to avoid bladder sludge. Layer pellets can have up to 6% calcium and ten to have a minimum of 4%) and far too low fiber (rabbits should have 20-30% fiber, chicken feed tends to have less than 10%). Some chicken feeds also have medications that can be deadly to rabbits or even meat products. Bad juju all around in regards to rabbits eating chicken feed. Grains tend to not be a big problem, just will make your bunny fat.
It sounds like she just hit 6-8 months which is breeding age. Rabbits get cranky and boisterous around this time, often being territorial. Sometimes the settle down, sometimes they don't. Just because she'd "never hurt" anything or anyone in the past doesn't mean that's the case now that she feels the need to claim and defend her own territory. In her mind she is making her space safer for her babies she expects to have, even though there is no buck around and chance of her having them. For a small prey animal the end goal is reproduce as fast as they can, so their bodies (and hormones, and behavior) react as if they will have babies, whether we say they will or not.
Think of the difference between the sweet little 8 year old girl that just wants to dance and play... That turns into the snarky, passionate, aggressive teenager that is abusive to her fellow students. It's the same hormones and it can cause a 180 in personality.