Sounds like you need to try a .44 Magnum. Heck, I'm not much older than you sound and my first handgun at 21 was a S&W 629 in .44 Magnum with a 6" barre. If you were closer, I'd take you to the range and let you try it. The only thing in .357 that comes close to the experience would be a light weight J-frame S&W, or maybe one of the new Ruger LCRs. The SP-101 is just heavy enough to tame out the recoil impulse. Actually, I enjoy shooting my .44, but my favorite reload is about equivalent to a full-power .357 in recoil, without the flash and noise.
Second, get a .22! You will enjoy shooting it more, more often, and the only way to get rid of your flinch is to work it out with dry-firing and low-recoil practice. You don't want to make it worse, or it will be impossible to correct in the future. And it's not a macho thing, I've seen big burly guys flinch when shooting their magnum revolvers and rifles.
And girls DIG shooting with .22s. Trust me. I have a couple of ex-girlfriends who enjoyed going to the range with a semi-auto .22 and would shoot all of the magazines I could load and hand them. And they were pretty decent shots too.
Lastly, double up the hearing protection. This will help more with the flinch than you might believe. Guns are loud, and humans are preconditioned to jump at loud noises. Training and experience help tone this down; I've seen people fall asleep behind a hot line at the National Matches, and have taken a couple of naps there myself... But just cutting the noise to start with helps tremendously.
Oh, and if you really, really want to punish yourself with recoil, you have to try a .45-70 Encore pistol. It's fun, in some strange way. I would do it again, but I won't buy one of them myself. All I can describe the sensation as is like catching a fast ball, bare-handed.