Cookie Clicker-likes are all mouse. Kittens Game is a good one. I also like The Tower, which is played on a phone vertically with one hand.

When I broke my arm, I found that I could still use the two split halves of a Switch controller.

Top down building games, like Factorio, Rimworld, and Timberborn can be played entirely with a mouse.

Balatro and Slay the Spire. For Balatro I recommend you look up the mod that adds more shortcut/mouse actions, that way it can be played more comfortably with just a mouse, tho it is not bad without it, just better with it.

Letting a mouse go and then smacking it with a paw.

I think Divinity: Original Sin 2 didn't have any parts that required a keyboard, and the combat is turn-based so it's fairly accessible. Great game as well if your gf likes CRPGs.

If she can use the right half of a controller, she can map the right analog stick to d pad, shoulders to confirm and cancel, and play lots of jrpgs from PS1 and earlier. A full PS2 or GameCube controller layout is possible if you have a controller with a paddle, using steam input or rewasd

Xcom was what I played while in a similar situation, turn based games were a life saver. Disco and Esoteric Ebb would both be good, I bet

Diablo and classic fallouts

I'm playing Mewgenics right now, don't think I've used the keyboard once. Fantastic game.

Old School Runescape(OSRS)

The only thing I can think of that requires keyboard is the chat which isn't required at all to play I usually ignore it myself,
keys in the game are just shortcuts for stuff that can be done via mouse.

The one thing that could be annoying is not being able to enter an exact quantity when depositing/withdrawing multiple copies of something from your bank, but there's preset quantity amounts that can be chosen by mouse only, so I don't thing that would become annoying untill higher levels

I got her Disco Elysium as well, that should be possible too, right?

Yes, I don't think you need to touch the keyboard. It's basically a visual novel.

If she wants to try something outside her usual genres, I think trying out a Civilization games might be a good option. Civ 5 and 6 can probably be gotten for cheap. The UI is completely mouse-driven, hotkeys are optional.

Slay the Princess! ...which is covered under visual novels

Point and click adventures.

Monkey Island 1+2 are great.

Broken Sword (the whole series) is great.

FTL: faster than light

Basically any point-and-click adventure

Most deck builders can be fully played with only a mouse. Turn based strategy or city builders are usually all fully playable only with a mouse.

I think Cloudpunk would be feasible with one hand, albeit more on the keyboard than the mouse. You drive a skytaxi through a cyberpunk city. The story is a 5/10 for a videogame but the vibes are cool, so maybe she'll be into it.

Into the Breach is a good one - it's a turn-based mech tactics game against bugs made by the same developers as FTL.

Read Only Memory: 2064 is a fun pixel art, point and click, first person adventure game.

Oxygen Not Included. - Takes some time to learn, but once you know what to do, it's pretty addicting.

VA-11 HALL-A - same universe as ROM:2064, but you play as a bartender.

Esoteric Ebb. Very fun RPG. Very Swedish, so don't show it together any Norwegians.

If it's only a week 2-3 long visual novels should be enough. Clannad takes like dozens of hours to read through.

The Longest Journey. Still one of my favorites 30 years later. Basically a point and click visual novel with some puzzles.

Of the Devil is a really good VN / courtroom battler.

Iterative games (cookie clicker-likes) are super low intensity and are near universally spreadsheet manager type games. Not the same genre she likes but certainly mouse only constrained

If she likes VNs I'll rec Umineko (~75hrs), featuring install advice from whyesseff. As far as "gameplay", it's reading (and listening to the music) while clicking through dialogue while occasionally checking the character and tips screens, with no choices or branching paths, and then engaging with and contemplating the mystery on your own.

BG3 and DE can be played with just mouse but not comfortably IMO. You need to use the keys to pan the camera around which is really helpful.

For those genres, Ace Attorney and Doki Doki Literature Club, in surprising(ly irrelevant) entry Undertale and Deltarune, these games don't even support a mouse but fully support one hand playing as ZXC also map to Enter, RShift and RCtrl

There are people who beat dark souls one-handed so I guess souls-likes

Diablo or anything like diablo, quite a lot of rts games, point and clicks and old rpgs.

It doesn't fit the genres you mentioned, but I just want to throw out Hammerfight, just because it's dope and you only use the mouse. In fact, you can play multi-player by hooking up a second mouse!

Its a little old so I'm not sure how it runs on modern systems or where to buy it. But it's really cool!

Also tbf, the action is a little frenetic, so it may be a bit much if the other arm is recovering, idk. Just a neat game that's mouse only that I've never heard anyone talk about, is all.

Narrative games, ala Suzerain or DE, would work well I think

Have a vague memory that Suikoden 2 can be played with just the right side of a controller, since it's only uses two or three buttons and the thumbstick, good for reading while levelling up against those damn rabbits.

Same for quite a few old-school games really, Xenogears might have been the same.

point and click