Really crazy ideas...

[Figment]

In your shoes, my criteria would be:
1. simplicity of rig
2. stability
3. ease of transport
4. rowing ability (we know how fluky the winds can be on inland lakes)

Keep an eye on the local classified ads as spring draws near, and throw a few hundred bucks at whatever meets those criteria.

Assuming you want to be in the boat with her, and so the obvious answer of "Optimist" is ruled out, the Dyer Midget leaps to mind. That may be a bit heavy for cartopping, though.

It will be tempting to find something that can also serve as a tender to your Real Boat, but that temptation will probably also come with a big jump in price.

[Tim]

They cost more, of course, but it'd be tough to beat the 8' Fatty Knees as a good learning platform. They are stable, roomy, and ensconsing thanks to their high sides.

The Dyer Dow is a ubiquitous choice too, though they are, upon reflection, horribly small and tippy--no doubt an opinion influenced by the experience with a Fatty Knees.

All this being said, there are any number of simple and nameless prams and dingies that either are, or can be, fitted with a sailing rig. These might well fit the bill.

Turnabouts are good learning boats too, but may be less easily transported since they are a bit larger and beamier. I also thought of the Opti, but that's really the next level, when she's ready to skipper her own boat (and even competitively).

Maybe YOU, Mark, are the one who needs that Beetle Cat, actually!

[Mark.Wilme]

Maybe I am ....

Nevertheless I am watching to see if I can't find something locally.Maybe a Tim boat shop, albeit on a much smaller scale !