Honestly, I'd go with the open source EmuELEC systems like the
GameForce or something like the RG351P. They can run every single retro handheld system game you can think off flawlessly, in general can run most retro consoles and arcade systems and even harder stuff to get working like the N64, Dreamcast and even the PSP (but with various degrees of compatibility, depends on the game when it comes to these three).
Also it is highly customizable, can use Wi-Fi and plenty of other goodies. (like running fantasy consoles like the Pico-8 for example or enhanced open source ports of various games, e.g. Streets of Rage Remake or the obvious improved Doom source ports)
Price is extremely affordable and can offer way more than most people will ever need. Also it is extremely easy to setup and get going, getting AmberElec up and running is a 4 step guide, anyone with basic PC knowledge can figure it out in about 5 minutes. (there is plenty of community support regardless, if you encounter problems)
So yea, this is the least convoluted way and the most convenient one of them all imo. Offers you everything you'd want in an easy to use format on newly made hardware. Modded PSP or PS Vita are also great options.
Nothing else is really worth it if she's just getting back. If somehow she catches on and becomes more serious, maybe then get some real hardware and everdrives, otherwise, I'd say just no.