Is this a "normal" behaviour for her or out of character?
If it's "normal", even at the extreme end of it for her then it's different than a one off.
I remember my normally very totally rational dd a little older than that screaming that she'd rather throw herself out of the moving car on the motorway than go to Dover castle. I don't think she knew anything about Dover castle but for some reason that day decided she didn't want to go. I asked her (now an adult) fairly recently what was actually going on that day and she didn't remember it at all (so obviously wasn't that traumatic), and thought it was quite funny.
So sometimes they can do something totally stupid without it being a sign of anything further. Nor did dd ever do that, or similar, again so it wasn't a sign of anything more sinister.
I'd also think that it was probably a case of the baby oil being to hand, rather satisfying to spray it and not knowing (and not really thinking about it) that it would do that much damage. My sister once emptied a toothpaste tube in similar circumstances. Luckily for her it was on the bathroom floor so cleaned up fairly well, but in the mood she was in when she did it, she wouldn't have thought about that.
Even the wardrobe: was that naughty or did she think she was doing a treat for you? Yes, she should know that she shouldn't paint it without checking with you, but I can remember as a child occasionally doing something I thought my parents were going to be absolutely thrilled with my helpfulness and finding actually they weren't too pleased.
I'd agree she needs a consequence. I'd go for the cleaning the wall. Depending on her reaction, possibly with you helping. If she has to clean the wall at a time which otherwise she would be doing something she likes, that's even better. Sugar soap will be fine for her to use as long as she doesn't spray it into her eyes or drink it.
If she refuses to clean then I'd be selling the iPad to pay for decorating things.
When she's calm have a chat to her about the consequences of such things. Pointing out that although she did it without thinking, the oil has made it far worse.
If it is a "normal" reaction to her, then check there isn't anything going on at school. She's just gone back, could it be a reaction to that? How was she over the summer holidays? I never realised how much stress ds (ASD) was under at school until lockdown. When the stress of school was removed he was so much more chilled about everything.
But also talk to the GP/school. Say you're concerned about her behaviour and take it from there.