Wifi escapes iPod daily when idling?

Hello, I bought 2 iPod touches for my girlfriend within the past half year. One had some pixel issues and eventually died. For the second time, instead of buying a refurbished one, since I had more money I just bought her a brand new iPod Touch. It's the generation that has the cameras but isn't the colorful $300 dollar ones. I paid $200 for it. She didn't use it up until a few days ago because she didn't want to waste the other one. This one has severe connection issues and it's really annoying since I cannot go to apple to fix it or replace it for at least until Summer comes. (personal reasons)

Anyways, here's what she told me. The iPod does this every single day, at every moment when it goes idle. At night the issue increases ten-fold and we're never able to talk via Skype or her text messenger app or anything else. Every application is dependant on the wifi.

Sometimes it can be anything from 1 hour at night, to 5-6 hours of being without wifi. It tries to connect to "guest wifi" *which is NOT a working wifi for the iPod touch.* Her main wifi is what the iPod should be connected to. The iPod either shuts off wifi completely or tries to connect to guest wifi. In the day, it takes minutes for it to go back to normal.

We really just want to be able to talk at night since we live quite a drive away from each other. Some nights both of us can only sleep 1 hour because we wait all night for it to work, only to fail or that we can only speak for a little.

That's about all the info I can give, since I don't really know what the heck's causing it. Also, I personally have never had such issues. My iPod touch, iPhones (3g, 4, 5c) and iPad 2 have never really had connection problems. Her other iPod was working on the wifi before-hand just fine (same generation) and the router wasn't changed suddenly.

Thanks to anyone who can solve this.

P.S. Her iPod came with iOS 7.