NetZero is Good and Bad. From a US person:
Good: Free, generally fairly good download speeds, ads don't take up too much bandwith usually (downloads on inactivity supposedly). Great for basic web browsing and limited downloading.
Bad: I've been disconnected for inactivity while *browsing* websites. Never ever, try to play ping sensitive games on it (ad downloads), 40 hour limit now before you have to pay for a advertising banner on your screen for $10 a month.
Juno is another free alternative I've used, and no limit yet AFAIK. Juno checks for your browser being open as a way to see if you are using the internet. Close that, and it will attempt to shut down your connection very quickly. I was however floored by the download speeds when I tried it out (Cable modem network was slow...2 second pings to yahoo are fun!)
Free ISPs in general: they block all POP3 email, except through their own POP3 servers. Juno goes one step further. It tries to intercept and launch it's own Juno email program.
If she goes over 40 hours routinely, I can recommend better ad free pay ISPs that go for $15 a month, no ads, no disconnections for "inactivity". Pridigy actually is very good in my experience. I can get $5 a month through an offer with AT&T worldnet (I have an AT&T Universal Card), if she stays below 150 hours, $1 each additional hour, though I have no experience with them.
I use DSL now however, so speed for me