I told her (maybe wrongly, in retrospect) that <Insert brain-dead question here> was a stupid question to ask a couple of times.
I agree that you were not bullying.
However, you say this girl is really slow. It is probable that she faces many challenges and frustrations every day trying to do things that you find effortless. Maybe in the future try to think about what things are like from her perspective.
This annoyed me because why should they get to play on game whilst every one else does.
You're looking at it as if they are getting a special treat by playing games instead of learning.
I recommend looking at it as "them crippling their education". Much of what you learn is built on knowledge that you've learned previously. If these people don't learn what is being taught today, when they get to future lessons they will not have the foundation to understand what is being taught.
If you continue to be frustrated by people getting away with playing games during class, maybe for some catharsis watch the old movie "Ferris Bueller's Day Off
" (but not during class!) and empathize with his sister's frustration with him getting away with everything.
I would be very grateful if you could give me any advice on what to do next.
This sort of reminds me of those situations where countries end up slowly being drawn into a war with each other when none of them want to go to war. I can see why you don't want this to keep escalating.
First of all, if they do report you, make sure that you get to tell your side of the story. A likely outcome will be that everyone will be disciplined equally.
Second, this behavior might not continue. You mentioned this happened under a supply teacher. The normal teacher probably won't let them act like that. I recommend that your first act should be to do nothing, and see if they also do nothing.
Third, if you do continue to have trouble with them, think strategically and consider whether a given response is likely to result in unwanted escalation.
Finally, if you feel that the conflict is about to escalate to a place where you really don't want to go, don't be afraid to report it to the school authorities. In that case, you should probably admit from the start to the things you did too (they will be given a chance to tell their side of the story, so it'll come out anyway). It is entirely possible that "being disciplined for what has already happened" is preferable to "letting things escalate to an even worse situation".