I am going to temper my reply with good tried and true common sense.
I and many others would agree that a 9 mm would be a minimum in caliber size for a primary combat weapon.
Yes there are many smaller calibers that are available but not with the proven track record of a 9mm ( most of the time getting the threat stopped quickly ) Bullet placement is key in all calibers.
Wheel guns are tough go beat in reliability. They do however lack capacity in most cases 7 round wheel guns are available and they will require more practice than an auto to be fast at reloading. Revolvers for the most part will be limited to a 2 inch barrel. There are a couple of S&W with a 3 inch that I like but do not own. I am not a fan of these small ones because they usually are not comfortable to practice with and beyond 7 yds accuracy will most likely suffer recoil and muzzle flash with a 357 is brutal in the dark. The 38 earned a nick name as a widow maker with many in law enforcement and that is why you don't see any one using them, back up maybe but not as a primary.
9mm most of the time can be had in larger capacity, can be a fast reload with less practice that an revolver, excellent +P loads available for defense, flatter profile making most of the time but not always an easier weapon to conceal. They can be had with a variety of levels of built in safety depending on your preference, which you may have yet to discover. Renting different firearms is fine if you have that kind of money if not I am going to make some recommendations. try to go to a large shop or store where they have a large selection and start by looking at them and seeing how they feel in the hand.
I would recommend a 9mm because of the easily managed recoil, proven stopping power with the new loads available in self defense, price of practice ammo at Wally World is $10.50 a box, this equals more practice and better proficiency with your weapon, either sex will find this easier to shoot than the bigger calibers most will offer an accessory rail that you can put a light on when used for home defense.
I carry a 40 Glock 23 compact it is not a small weapon nor is the recoil light, but I have shot and carried most of my life. However I like the following manufacturers: Sig Sauer, Glock, Sprigfield Armory and Kahr. You can certainly by custom and spend more but I would not advise it as a initial purchase. I make the above recommendations because I have owned in all 3 and have never come up short with any of them. I personally feel you would not go wrong with a 9mm as a great starting point and you would and should feel that you are not under gunned if you practice and are proficient in its use.
This reply was not intended to start any arguments and I am certainly not the end all, know all authority. Just my Opinion.