That was a long OP.
Obviously you’re not in the wrong, and you wouldn’t have been even if you had initiated the dismissal. There’s a reason why entering a coworker’s space is forbidden that has nothing to do with violating personal space or bullying behavior: if she had seen personal information from anyone on your desk, it could have been a potentially catastrophic data breach. No doubt your assistant manager boss who witnessed her in your space was worried about that.