Hi Karen,
Oh the woes of potty training! First of all, congrats on the poo on the potty. That's a good step. Secondly, it might be a good idea to invest in flushable wet wipes. You can get them at the grocery store and teach her how to judge when she's all clean.
While fecal matter in the vagina is not good news, it cannot cause a kindey infection. Bacteria has to enter the urethra first. This is a very small passage and close to the bladder. If a child develops a bladder infection, she'll have a fever and she'll feel the need to pee often. She might not pee even though she has the urge and when she does, it will hurt. The bacteria has to travel past the bladder into the kindney in order for a kindey infection to develop. By this time she would likely have a high fever and general malaise. Her back might hurt and it will hurt to pee. Kidney infections are nothing to mess around with. If you suspect this or a bladder infection give her some serious liquids to drink so that she can flush the tract often. Take her to the doctor quickly. She will need antibiotics at that point.
The urinary tract is a sterile environment and it keeps itself so by flushing itself out ever few hours. Make sure she is drinking a LOT of liquids and peeing often. That's the best defense against a Urinary Tract Infection. Also, teach her to wipe from front to back (hard with a child's short reach, but necessary) not back to front.
About the left-over fecal matter, it might be a good idea to wash her in the shower after a poop. I know she might resist, but it is better to force that on her than to pay hundreds of dollars in medical bills if a bladder/ kidney infection does come up.
Generally it is E. Coli bacteria that is found in the feces that causes these infections. The terrible thing is that this bacteria can double its population every twenty minutes so frequent urination and copious amounts of liquids are necessary to combat it.
I think, though, that teaching her to wipe from front to back, giving her plenty of liquids and imposing the shower -after-you-poo rule is a sufficient to keep her healthy. Also, consider showering instead of bathing. Swimming around in E.Coli isn't sanitary. In addition to not being something we want in our urinary tracts, it is also something we do not want to get in a cut or enter our blood stream or entering the mouth. It is fine in the recutm, but no where else.
Good luck with the potty training and congrats on the potty pooing!