Ummm... If she can teleport, doesn't it negate her alibi?
Technically, yes, but the prosecution would still face the reality it's an accusation with zero proof against an alibi that does exist, even with a caveat. Silviana can officially prove she was in the dungeon, so the prosecution would need to prove she purposefully teleported away from the dungeon to push Katia down the stairs, and then went back to the dungeon to finish her work. While Katia actually has no wound under those bandages or nothing else to show for the suggested assault. So, it's not merely a word against word because Silviana would have needed to go out of her way to do it, interrupting her legit adventurer's work.
This clearly is different from a situation where both Silviana and Katia would have spent the whole day in the same academy buiding. Since Silviana was spending the day elsewhere, she wouldn't have even known where Katia is or if she's ever near convenient stairs, all alone.