Hacker virus on an iPhone 5s

Hi guys and gals. I'm currently spending the day at my boyfriends parents house and in the middle of the day, his sister's iPhone 5s kept doing what looked like a pop up blocker on her phone every time she tried to go on to safari. What I thought looked like an ad for some "new game" on the app store continued to ask her to purchase a virus software for her phone. This "pop-up" or "ad" also had a name and email attached to it, that wasn't the name or email that is attached to her iCloud or her iTunes account. Is it possible to have a "hackers virus" put on to someones phone without downloading an app or going to a safe website? Someone please help ASAP!!! I need help!