So I have a router and I was wondering if I created a guest network for my sister and I put a password on the first one if it would throttle or reduce internet speed with 2 wifi networks. My sister was on vacation for a month, and during that month I let my mom borrow my xbox and it has a wireless adapter so she connected to the internet and I was on my PC. I played all games no lag at all. It was as low as if I was home alone. But as soon as my sister gets back, the internet went to crap. I'm not exaggerating at all. The internet is so terrible now. She only uses her phone too and I don't know how its possible to use that much of the internet on her phone. She is on it from the time she wakes up which is around 9pm till around 2am. She lays in her bed all day and is on it non stop. Please help I need to know. I also havent been downloading anything, no games nothing on steam. All I do is have one thing open at a time I check task manager too.