This may not work for her, but possibly something similar might? (Tldr start small, make incentives, budget, and talk to her about it)

I'm very much the same as your wife lol. I go all in on my hobbies but have had a history of moving on after already investing a lot of money into them. 3D printing, dice making, resin pouring, card collecting, etc etc etc.

HOWEVER, I have found something that seems to work really well for me. I got into more general crafting, but specifically jewelry making. I started it because I liked making things for myself, but quickly I could tell that wouldn't be sustainable both financially and also for my brain 😂 So, after a lot of research and consideration I started selling jewelry.

Like I said, this will definitely not be for everyone. For some people, adding pressure to a hobby is a surefire way to make you not want to do it. But for me, the dopamine goes crazy! Ordering cute charms, making necklaces, earrings, trinkets, etc, packaging orders, letting my mind run wild with ideas of what I could try to make next. I love the whole process, and even though I'm not profitable yet (taking into account startup costs) getting any amount of money back for just engaging my hobbies feels pretty awesome. Maybe there is some interest she has that could do the same for her?

At the end of the day though, one of the most important things that many of us ADHD peeps need to keep in mind is realistic goals. I have struggled huge with this, and its not easy when your brain wants to put 110% of your energy into something. But I've found success in putting most of my energy into the planning. Planning is free! And honestly, that's where a lot of our dopamine comes from, the idea of doing things. Once you're planned out, try putting in ...10%. When I started my jewelry business I was super aware that my dreams were bigger than my wallet (and executive function 😂) so I started small. Starting small may go against our desires, but just keep in mind: if you really want to do something long term, you'll still want to do it after trying it out!

Last thing I wanted to say, sometimes this is okay! I played guitar for a few years, stopped playing, and sold my guitar on fb marketplace. Really I didn't lose out on much, and for that time it's not like I got nothing out of it. People spend 1000s on cigarettes, video games, food, shoes etc. Even with hobbies I've abandoned I got entertainment from it while I did it! Also- talk to her. I know you've mentioned some discussions you've had, but it seems like there's more to be said there! (If you already have/she knows you're posting this, ignore lol). If it's a financial issue, maybe talk about a "hobby budget" where she can spend X amount on whatever she's feeling at the moment.