Gamecrash / High Ping Problem

[TH00R]

I play this game with my girlfriend for over 200 hours. We bought 2 gaming laptops, that are exactly the same, and we play via wifi. I host the game and have normal ping, no problems. she joins my game, every 10-15 minutes she gets a high ping and every 30-40 minutes she gets kicked out of the game and sometimes I have to remake the game, because she can´t find it anymore. Sometimes, she sees herself on her laptop on another spot, than I see her on my Laptop. 

Does anyone know, how we can fix this?