if your child had contracted hsv2 from you, she would've been very ill within the first few weeks of birth. you have no reason to worry at this point that your 3 year old was infected during birth :)
The risk of transmission of the mothers genital herpes to her baby through vaginal delivery is 0.2% or less. A c-section would result in this being zero or something very close.
How common is a regular c section birth to aquire herpes?
No herpes would not spread down the placenta. Most likely there would be an issue with an infection at birth. A blood test would remove any doubt you may have, it will be negative.
You don't think it makes it way thru nerves into the placenta or anything that could affect a child? After three years if something was going to happen would it have happen right after child birth or affect the child years later?
The virus will not generally exist outside of the infected ganglion. A c-section virtually removes all infection risk.