Sorry I can't be much help as mine are all indoors and currently have no access outside (hoping that might change soon but we'll have to see), however I can't say I've personally heard of them getting sunburn. I could be completely wrong though!
Are you sure she doesn't have mites? Flaky skin can sometimes be caused by them, and redness could be from scratching. They're very small and hard to see, you have to look deep in the fur and watch closely to see any sign of them moving around. I had a vet think I was crazy as he couldn't see them no matter how hard I tried to point them out, even though I could see them crawling around :roll:
I would personally never use human suncream on rabbits as it's intended for humans not rabbits and rabbit skin is incredibly delicate. Plus it may contain harmful chemicals if they lick it off (which being rabbits they're almost certainly going to do :roll
Aloe vera I
think is poisonous (could be wrong).
I know there's a tea tree cream thing that P@H do but if I recal I was advised against using it when I asked a little while ago (Jazzie had some very irritated and painful ears after emergency treatment at the vets, poor girl was badly bruised and irritated from all the needles)
Sudocreme is, to the best of my knowledge, rabbit safe and I've used it several times on hocks with good results but I'm not sure about using it on ears. I would wait to see what others say on that as I'm not sure.
I'm sorry I can't be more help
Hopefully someone will answer soon with much more knowledge than me. I'm afraid the only thing I can personally think of is to ask your vet, but as I say I would check her well for any mites as that's what it sounds like it could be to me personally