Set her up as a local account first, then add a Microsoft account if she wants to get the full use of the Metro tiles.
Figure out if there actually IS a lot of bloatware on the new computer. See if anything on there is stuff your mom might want before you decide to nuke it all.
My new Dell laptop wasn't loaded down bloatware. The usual stuff (Quicken, etc) came on a separate disk for me to load or not.
Make a backup.
Upgrade to Win 8.1.
Make a backup of that.
Run Windows Update.
Make sure that Windows Firewall is turned on.
Install an anti-virus program, if one isn't already installed. If one is, check to see if it is one that is rated highly by the membership here. Check to see how long its subscription lasts. Set any AV program used to auto-update. (Check out Purplus for software discounts.)
Install Spyware Blaster (free).
Install WinPatrol (free).
Buy and install the Pro version of either Malawarebytes Anti-Malware or SuperAntiSpyware so that it runs realtime (only the Pro versions do so). Set it to auto-update. Install the free version of which ever program you don't buy, to use as a secondary manual scanner.
If she's going to use the laptop in public places, install Zemana Anti-logger or another anti-keylogger.
I'd recommend installing Pale Moon as the browser, with the following extensions:
Adblock Plus, NoScript, Disconnect, Flagfox, WOT, NoSquint, QuickWiki, HTTPS-Everywhere. Pale Moon will remember passwords if you want, but make sure that a Master Password is enabled. Otherwise install one of the other password managers so she can use complex passwords and easily remember them. I've used Password Agent for years: »www.moonsoftware.com/pwagent.asp
Whichever browser she uses, check the various security settings. Don't accept third party cookies, turn on "do not track". Set permissions high enough to protect but not to interfere with normal usage.
If she's been using computers for years, install Classic Shell so she has the option of a familiar start menu if she decides she's not into the Metro tiles.
Depending how computer savvy she is, decide whether to set Windows Update and Flash to auto-update or just notify of updates. Ditto with Java.
Install VLC player, since it will play everything.
If she's into ebooks, install Calibre with Apprentice Alf's plug-ins. That will strip the DRM so she can convert Kindle books into epubs and vice-versa, allowing her to buy ebooks in any format and be able to read them on whatever ereader she has (if she has one).
Install 7-Zip which will unpack most compressed files.
Check her cable provider to see if they have a PC app that can be installed to watch TV on the laptop.
Install LibreOffice (free) if she doesn't use the Microsoft Office suite. Win 8 doesn't come with Microsoft Works so there's no free basic Word-type program installed.
If she likes games, get her a subscription to POGO and put a link for it on the desktop.--
Patriotism is not waving a flag, it is living the ideals
I want to retire to the Isle of Sodor and ride the trains.
Life is just better when Jeter is in the lineup.