No, you don't have to even touch the original profile. It sits there together with the new one, and you can select them every time you start Firefox.

How to Create Multiple Profiles in Firefox

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Oh, thanks. I'll try that.

Well it doesn't show an error along the bottom line, and I tried several things (disabling DNS prefetching for HTTP and HTTPS, backing up the profile - which didn't work since there was an error copying the folder, and restarting with addons disabled) but none of it worked. I also looked in the settings and disabled a bunch of extensions manually, but that didn't fix it either. What could be wrong with it?

By the way, that computer is a horrible POS with all kinds of garbage installed and configured badly, and there's Norton or McAffee (the owner insists on using it) and some other junk, but I didn't even look into all of that, though supposedly none of it has changed since this problem started occurring, but it does seem to slow everything WAY down.

EDIT: And by the way, it does show pages from the Mozilla website, whether I navigate with links or type them in manually, so it seems as though Firefox is somehow configured to only show that website and nothing else.

It sounds like a situation where you either charge double or cut and run. Depending how much administrative control you're able to gain.

Maybe show her via a Linux Live USB that it's a her problem. :p

Allow me to introduce you to LibreWolf:

https://librewolf.net/ ..a warning, though:

"No DRM content" online can be disabled and you can watch it if you manage to set it up.
That being, Netflix, Prime video, and so on..

dnovraD, I'm not charging for this, but it's something that I need to do, but how would Linux be relevant to this situation? Maybe I'm misunderstanding you.

.Keys, I'm not sure I understand your warning, due to the wording of it. Could you rephrase it perhaps? Are you saying that if I manage to set up the browser (as in install it - is it hard to do?), or if I manage to set up the configuration to disable "No DRM content" (thus implicitly enabling DRM, right?) then I can watch "it", as in watch Netflix, Prime, etc., because they have DRM in them?

Well ideally, I'd like for there to be no DRM at all, but I don't know whether a bit of it would be unfortunately necessary here or there.

EDIT: And also, is there a chance that installing or using LibreWolf might interfere with any other preexisting browser? I might want to install it on my Linux computer, but it already has Firefox. Is this thing made by the company that made LibreOffice?

Sorry if my wording was bad. I will try to rephrase it.

Many sites nowadays use some kind of online DRM technology to witch your browser must confirm you're logged in to be able to watch its contents.

By "if you managed to configure it right" I meant that LibreWolf (and other browsers, apparently) had problems in the past with "Widevine", one of these DRM technologies. The problem was related to different Widevine updates or versions, making DRM content unable to be played on LibreWolf/Firefox/Chrome browsers in the past. Some users still have this problem and can't watch DRMed content through their browsers because of this, some users managed to fix this problem and watch Prime, Netflix, and so on. There are some articles and posts online on what this problem is and how to fix it.

If you don't watch anything DRM related at all, LibreWolf is perfect but it uses Firefox security online features and adds more, also enabling security features disabled by default on Firefox.
As with any browser, you can export your settings and bookmarks to then import them in another browser, so, no, I don't believe LibreWolf will interfere with your other browser.

Though, of course, I recommend you testing it first for a while before fully replacing Firefox with LibreWolf. Use both for a while and compare.
I've always used Ungoogled Chromium in the past, and, coming from that, I do prefer LibreWolf, for your to have an idea where I came from on this term.

LibreWolf is not from the same company as LibreOffice, it just uses the Libre to signilize its principle - "Being Free" online, and all the FOSS mentality about privacy and so on. :)

Well I'm not really sure whether that computer is viewing any DRM websites, but if it works on Firefox then it should also work on LibreWolf, if I understand what you're saying, since it was a problem in Firefox, so the same problem would have been in LibreWolf, right?

But since Firefox isn't working for whatever reason, would the same problem likely be present in LibreWolf, or not, simply because it would be configured differently?

Only if the antivirus that she's using has seriously screwed up her system. Firefox and Librewolf, while using similar (near identical) technologies, would of course store things in different places.

Well the antivirus has probably screwed up a lot, because it's been running slowly for a long time.

And why do you suppose I get an error when I try to make a copy to back up the profile folder?

Depends on the error. There's a non-zero chance that a "user" aside from her has taken control of the folders, or that the antivirus is "protecting" it, since it would be considered "important".

Though, that's speculation, since I'm comfortably living in an operating system where seizing control is one carelessly typed command away.

Well I really doubt there's any malware on that particular computer, but even though there was an error code (which I don't remember), it said that the error is unknown or unspecified or something like that, so I don't think there's any way to know what it is. I was just wondering why copying a folder should cause an error, considering that it's not like I was trying to move or delete anything without the correct file permissions, and copying doesn't affect the original.