If I can spare an advice - save your money. That Athlon is even at stock speeds way too much overkill for office work.
But if you definitely want to spend your money, ask your mom if she's annoyed by the sound of the CPU cooler. And if she is, then get her some good <65W processor with a passive cooler. And also get her a passive cooled PSU. That would make more sense to me than upgrading a perfectly fine overkill CPU
Well I was thinking of upgrading mine to the 8350 only because my moms computer is still using the 955BE OC'd to 4.0GHz. I planned on giving my mom my FX-6300.
If your mom needs an upgrade, then by all means, take a step up yourself.
If she is encrypting documents for security in her work for the law firm, she will see a HUGE decrease in time spent doing that. If she does a lot of power point type operations or video rendering type scenarios even monte carlo sims...she will see an upgrade in performance over the 955 by upgrading. If she multitasks a lot it would benefit her as well...(i.e. 3-5 different programs running at once to get work done)...she would likely see some improvement too.
If she does none of that...it may be overkill.
If you do alot of hardcore gaming, and multitask alot and feel you want an upgrade...then go ahead...you'll get a bump in performance and your mom's PC will get an enormous boost.
Just an FYI a 955 @ 4.0 is better than a 6100 in most tasks including gamming
If he was using a 1090T or 1100T or 980BE @ 4.2ish...I might agree...if he was using the FX6100...I might agree too.
But the FX6300 @ 4.5 is an upgrade over the 955 @ 4.0...even in gaming benchmarks...look at Tom's benchmarks between the 2...the FX6300 over the 955BE at stock is better...with a 500 MHz advantage OC'ed it would still be better.