Question on Family Accounts

After initially being waitlisted and assuming/accepting that I likely would not be one of the chosen ones this calendar year, I was bumped into the reservation queue and allowed to order - my steam machine is packed and awaiting pickup from the shipper, and I cannot wait!

I have a couple "main" reasons for wanting this. First, I've been accruing a large steam library over the course of a decade plus. I love management sims, and I have a once-powerful-enough desktop for this purpose. However, I'm really not a PC guy. I've been primarily a console person over the years, because I don't have the patience or know-how to build and/or tinker with PCs. I don't mind fiddling with graphics settings, and am used to/comfortable with doingthis thanks to Steam Deck, but when it comes to component-swapping, it's too much for me. I also have no desire to upgrade that PC because I just don't enjoy gaming at my desk - it makes me feel isolated and sort of feels like work. Steam machine allows me to migrate this massive library to the living room, which is enough for me.

The other big reason is my wife. The steam ecosystem is perfect for her, as she's mostly into "cutesy" indie games, often narrative focused, and often with that cute/creepy Tim Burton/Del Toro vibe. Steam is overflowing with these types of games, and they're often cheap - and the refund system means she isn't punished for trying out an indie game that looks appealing to her but lacks much marketing or info, and winds up being disappointing.

The problem: she has no steam account. While she's played one or two games on Deck that I picked up for her and never intended to play myself, that's now going to change - I have games in progress or complete, where I don't want progression affected or achievements unlocked that I didn't earn...games like Dispatch or South of Midnight. She will want to play those - so my plan is to help her get a steam account and try to link it as a "family" account with mine. So my question is, how does this work? I've done a little research, but I'm just looking for anyone with actual experience here. There are lots of situations where we might be gaming at the same time - one on deck, the other on the machine...I have accrued a treasure trove of indie games for her over the years that she just hasn't had an easy path to access consistently. Anyone with experience with family accounts, I'd appreciate any info you can provide!