Agree with many about the short first flight- preferable early in smooth air although you may be contending with the marine layer. Just some sightseeing and stopping at an airport with a decent restaurant that is not your home airport. Maybe French Valley could be a good first quick flight to a restaurant and back. Has a decent airport vibe there but uncontrolled field can be busy so be on your toes coming in to the pattern.
A few suggestions with pros and cons for when you eventually work up to a destination or if you decide to go for it:
Catalina is great but the approach can maybe freak her out on first time due to the runway being on a cliff and looking short and being over water etc. You have to take a shuttle down to town (does she get car sick- roads are twisty turny) and there is lots to do. Zip lining, jeep tours, hiking (requires free permit ahead of time), snorkeling (you can rent wetsuits there), boating, kayaking etc etc.
Big Bear is fun for hiking and lots of other stuff to do. Will be probably nice brisk weather good for getting outside and moving if you like that sort of thing. You can find lots of hiking or biking trails, there is an alpine slide (yes fun for adults even!), and there's always the scenic chairlift or boating on the lake. Cons would be if she doesn't want cooler weather and also it can be bumpy flying into the mountains and you want to make sure your plane is capable due to the somewhat higher DA than you are probably used to. Definitely good to run performance numbers and research local procedures.
Santa Barbara can be a nice destination. Airport is 10-20 from town and uber is easy to get there. Great views flying up the coast. You can get a bit of the rockstar vibe parking at one of the fancy FBOs there....
Santa Ynez and Solvang are great. Just took my kids there and made this video- hopefully it gives you an idea of what its like there....
Let us know what you decide and we can offer more local tips on the destination.