But football players are doing stuff like this all the time
That sounds like something a child would say when caught doing something wrong "I didn't do it but he did it as well" . Hardly the way we should be encouraging anyone to think about their actions when someone does something wrong.
It's not great but she hasn't badly hurt someone
Again, not only is that not how the law works - you are, and should be punished for the intent, not whether the person ducked out of the way quick enough.
Someone can be badly hurt in a complete accident (in a match that could be a clash of heads, for example), or lucky enough not to be hurt when someone intended to hurt them. Any charges are based upon the person's intent. If a player slides in with studs showing, for example, they (quite rightly) get sent off, as they intended to commit what could be a career ending foul, whether the intended victim managed to leap out of the way or not.
I thought it was a shame that she was banned from the quarterfinal, but I'm actually devastated that she's banned from the semis as well. We NEED her, and this could cost us.
Well, clearly we don't need her, as the other 10 players fought on brilliantly without her for the next 40 mins. She could have cost us the game, and the tournament, and it is credit to Serina's tactics, and the other players' discipline and energy and stamina that they managed to hold on.
and she is very contrite and apologetic,
No she isn't - or at least as far as anyone is aware. She put out half an apology (which every team would have made sure the player did, to limit damage). I mean, she might be - none of us have any idea as (quite rightly) she is being protected from the press and has turned off her social media. I presume she does regret what she decided to do, as it means she hasn't played, in the 1/4s and won't play in the semi's, and who knows, if we get to the final.
I totally agree with @girlfriend44 and @Jo1405 .
Nobody is 'berating her' or 'going for her blood' but let's not pretend this was acceptable, or - as I have seen in so many places was "stupid because of all the cameras ". It should be condoned as being a dangerous assault, whether the cameras were there or not and whether you have seen other players do it or not.