unsure

my rabbit gets along with one of my cats fine and often chases her around the garden but there's been several occasions where my cats been sat at a higher height and my rabbit will stand still staring at her and stomp her back feet. why is this??

Think about it from your rabbit's perspective:

On the ground both your cat and rabbit are at an equal height, so one doesn't have an obvious advantage over the other - your rabbit feels pretty comfortable. However when your cat is up high, the situation is very similar to one that would occur in the wild. For example, a bird of a prey eyeing up a rabbit. Your rabbit is trying to figure out whats going on and whether or not there's a threat. She will stomp her feet to warn other rabbits in the area of the danger, allowing them to get away.
Hope this helped!

My rabbit and cat get along well too - isn't it just the cutest little relationship?!

thank you for this!! I knew she must be intimidated. I haven't had her long and getting to understand her behaviour is great it really is the cutest, such an unusual bond