There are far more reliable rounds out of a pistol than 22lr, and that amounts to every bit as much of a "performance" issue as the lack of size/ballistics/power. But a reliable 22lr pistol with reliable ammunition (CCI) isn't necessary a bad option. In fact I think it can be a solid choice under the right circumstances, which might include your wife.
Check out the Ruger SR22. It's darn near identical to the Walther, but I believe it costs a bit less. Mags are also a bit more affordable and easier to find. I helped my mother shop for her first pistol and that's what we chose. It's very compact, fits small hands well, accurate, and a highly functional gun. To this point I have seen zero failures even with bulk ammo. And the gun runs about $300, with very light, compact, and affordable rail mounted lasers available if desired. I bought mom a Crimson Trace for Christmas...$110.
FWIW- The dealer we bought the SR22 from told us they'd stopped carrying the Walther P22 altogether because the SR22 was so similar, but more desireable (USA made, lower cost, brand loyalty, etc).
"The Future is Unwritten"