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Doesn't need a software firewall as vista has a decent one...
Hopefully she has Broadband and either her dsl or cable modem does NAT. Make sure it's on.
If she has dialup...probably don't need any type of FW other than Vista's.
As for Anti-Virus...I get mine (sophos) free as a campus employee...
If I had to buy one, I would ABSOLUTELY stay away from Norton and McAfee.
I paid for and used this one for a few years and was pretty happy...
http://www.kaspersky.com/I almost got this one, and would recommend it as (at the time) seemed like a very stable, friendly (not a resource hog like most) AV.
http://www.eset.com/ (nod32)
Hope this helps.