Funny, my long-time girlfriend had the same idea. She bought a Tesla Model 3 LR AWD after experiencing my P3D- for a while.
If you don't need much range, the BMW i3 is a nice car, and one very unique thing about it is that it's SMALL. I love small cars, but there aren't many small BEVs with any decent range. I know there's a smart electric, FIAT 500e electric, Honda e (which we cannot get in the States), and the BMW i3, so I consider this a fun selling point. As mentioned in this thread, Tesla has their own 25k car coming at some point in the near future. Will this be a hot hatch of some sort? Remains to be seen, but it's gonna be great and I hope it's nice and small and with good range.
However, the i3 is fairly expensive. I think you *could* afford a Model 3 more than you realize, especially by the time you get through a few options with the i3. I priced out some trims on the i3 and it got expensive quickly, but I too have a soft spot for that car.
If you're open to a Model 3 refreshed SR+, I think you might be able to swing it with the Subaru trade-in, and your wife could drive that. The refreshed Model 3 has 263 miles of range, and its no-nonsense pricing (before rebates and electric savings over gas) is $37,990. Plus you'd get that beautiful M3 styling.
I'd also look a Tesla Wall Connector since you have a garage. This would be ideal for two Teslas. It's less ideal for a Tesla and an i3 but you could always just go with a generic L2 charger from another company such as Chargepoint or Clipper Creek once you have your charger installed. Then, either of you could use it without an issue as long as there's a J1772 connector—you with the adapter that came with your Tesla and she could plug in to the i3 without any adapter.