Samsung Galaxy sIII neo wifi problem?

So my sister has Samsung Galaxy sIII neo, and she goes to facebook with it very often, and when i am playing cs:go and shes connected to wifi with her phone the ping goes up to ~500 from 50, and slows down the internet in the browser on pc, it doesnt happen with my Lumia so i how could i fix that problem. Tried forgeting the network and connceting again.

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