Having Pop-up problem can anybody identify?

[I need a life]

So, I'm typically very safe with my own things but, my mother's laptop seems to be having a problem. Every time she browses the internet whether she goes to Netflix, Vacation websites, or anything else, she has a pop-up. Oddly, this isn't consistent as it only happens every 15-20 minutes apart. i.e she doesn't have it continually on the same site.
I initially thought she might have an infected pc. I installed Adblock to attempt stopping the forced pop-ups. I also installed Norton and did a TrendMicro scan but, found nothing. I've checked the Installed Programs for anything sketchy but, haven't found any of the typical programs. Also, I've cleared her cache and web page data.
This is simply becoming a problem because the only thing I can tell her is to exit using Task Manager since it locks her in the webpage.
Any ideas or thoughts are appreciated.

 

[scout_03]

you need to do a full virus scan without network and in the browser set to not have pop up also the do not track option also do a ful malwarebytes scan .

 

[AdJaBr]

Are you able to post a screenshot of your popup

 

[br00n0]

Have you tried Malwarebytes? My father-in-law had a similar popup problem and was fixed by that application.

Good luck!

 

[Paul NZ]

Adwcleaner may also remove it