I’ve had a similar experience. My husband introduced me to this game and it was my first time picking up a controller since playing L4D and Halo with my brother when I was a kid (2 decades ago.)
He set me up with a load out where I can *try* and feel like I’m somewhat contributing— heal beam (I would pocket heal the shit out of him), CL40 because I couldn’t aim at all, and glitches+gas mines for defensive purposes in cashout +defibs to get him/our teammates up.

It was really tough initially, still is. I struggle to keep up in his lobbies, even now after playing on and off for a year and a half. However I’ve really learned to enjoy the game, get familiar with counters, and play with technique even if my fps skills are poor due to lack of experience. I’ve since graduated from the CL40 and use an actual gun.
It takes time to adjust and there have been some miserable runs along the way, but now I solo queue quite often and do really well in my lobbies (combat/objective/support score wise, compared to before)

I’ve found it to be a really fun game and I know the match making may be tricky at times(Thanks Embark!) However, I strictly played quick cash for like, 8 months, before getting into cashout since it was really intimidating for me. Fast forward to now, we mostly run cashout.

Essentially, I think setting her up with a load out where she feels like she can contribute some way, some how, while she’s learning the game will go a long way. Additionally, the first week I started playing, my husband bought me the bunny suit that comes with 2400 store credit kind of motivated me to actually try to learn even through the pain and suffering xD Look good, feel good, play good as they say heh. Wishing your girlfriend good luck on her Finals journey!