Excellent choice in a quality revolver. I'm sure you will be pleased.

My girlfriend prefers the 4" version over the 6", claims it 'balances' better. It is a highly subjective area to be sure, but I think with a light recoiling revolver like a K-frame 22LR there is little need for the extra barrel length unless one plans to do longer range target shooting or perhaps shoot metallic silhouettes with it, and she finds the 'back in the hand' feel less fatiguing for a longer shooting session than the longer barrel. We enjoy shooting metallic silhouettes (informal for bragging rights among ourselves, not as a competition but they will certainly do well at it) with my 6" 17-8 (it has a full underlug barrel like the 617) and find hits easier to make at longer distances with it however.

WRT to sights, I find that the dayglow type sights do not work for me. There is to much of an interfering aura around them, they provide a very indistinct and imprecise aiming point and are difficult to align precisely in the rear sight.

While I do not think it possible to distract anyone from a finest quality firearm like the S&W Model 617, I also would plug the Ruger Mark III standard pistol in stainless steel with a 4" barrel. This was apparently a special run and they are drilled and tapped for a scope mount. She got one of those, I fitted it with an inexpensive Bushnell TRS-25 red dot scope and that is singularly one of the most remarkable small rimfire pistols I have ever shot. It is boringly easy to shoot standard 1/10 smallbore rifle size pig and ram silhouettes from a standing 2 hand hold at 50 yards with that pistol.

__________________
" I said, good DAY! "