A lot of DSL modems actually have routing functionality that interferes with your actual router. They tend to use a PPOE setup, which means you have to tell your modem to not do PPOE and use the settings that it had to tell your router it's a PPOE connection, complete with the login user/pass and external IP address the modem was getting. I know that sounds complex, so maybe just google on that subject with some keywords and you'll likely find the steps for it.
OK...I can give noscript and ad block plus a try on Firefox. She is using the most current version of Flash. I try to keep all of that up to date. I've got no experience with these Firefox add ons however.