Should I speak to her about it?

So I'm m14 and I've been meeting a girl lately, now she behaves differently when we meet and on snapchat than when we play with friends on PS 4 (that's rather stupid there), should I speak to her / write to her about it, if yes how? E.g. I wanted to ask you something, why do you behave differently at the meetings than at the ps4. Or should I mulate it differently.

Of course, if you behave differently, speak to her! There's nothing to it. The question can still be fine-tuned, but in itself it is legitimate!

How could I put it roughly?

Try to avoid every filler word. Articulate yourself briefly, concisely and clearly. Something like "Anything going on? Are you acting weird online?"

Talk to them!

If it makes you feel uncomfortable, I would address it… I mean, if you like her (whether friendship or more does not matter) then I would address that otherwise it might be too late at some point.

maybe she doesn't even notice it herself and will pay more attention to it afterwards and if she does it on purpose she's stupid anyway: /

Thanks for your answer but when playing it was more related to my friends

Thank you, could I ask the question like this or should I leave it unformulated

Hey [name]. So I noticed that you behave differently in real life etc. Than when we gamble. Is something going on?

I would say something like that.