Inappropriate risk taking and disadvantageous decision making are major characteristics of ADHD, and she has shown both of these.
You mention the same jump despite a terrible result the first time, running across the road instead of waiting for the lights, not taking in the instructions in the exam, not understanding what happened to cause her disqualification.
Also this: ...she can have a gob on in an argument , shout out sometimes , talk a lot and she definitely buys useless things without a reason but I’ve never really seen it as a problem.
Weirdly , she buys things without a reason but can also be indecisive about things at the same time and I think she realises she can’t do physiology ect if she carries on but she either has a very cocky attitude about things as in she knows she will pass or genuinely doesnt realise.
Above all, bells are ringing from the failure to learn from a previous mistake. You seem sure she won't learn from previous mistakes so I am assuming you have seen many examples.
Wrt discomfort when all is silent around her, she may have an anxiety problem too.