I am computer "capable" by trial and error - but not technically trained and never seen linux in my life. My experience a few weeks ago installing Ubuntu was that you can easily install it and use it immediately out of the box, however if you use the use the web regularly, you will have work to do. That is because it does not include the common video and audio codecs and plug-ins required to enjoy video and audio on the web. Same issue if you want to play mp3s and watch DVDs.
Finding out how to install these codecs and plug-ins is a nightmare, because Ubuntu does not support these, you have to trawl through lots of Forums checking the information you read very carefully for relevance to the version you have, and give consideration to many different possible options.
Having spent some a few days trying to get everything needed, I had only succeeded in getting DVDs working. BUT THEN whilst searching for more ideas on what to do, the answer arrived "Linux Mint", a Linux distribution adaption absolute ideal for your Grandmother - especially if she is only on a small pension!
My next step is to make a donation, because you have saved me a lot of time, frustration and heartache.
Thank you to all you Mint developers and a very Happy New Year