Unfortunately, I know nothing of Susanna or her karting.
Looking in my copy of "Chi E' nell'automobilismo italiano" (900+ pages printed November 1964 and received as a gift some years ago from Corrado Bellabarba ... GRAZIE!), I found two index references to Cesare Raganelli, probably Susanna's father? Unfortunately, the index reference to page 386 seems incorrect but page 210 shows "S.C.A.R." = Societa Commercio Automobili Raganelli in Roma. Looking at pagine bianche (white pages online), there are 15 listings for Raganelli in Rome and three seem likely to be hits. #9 is Susanna, #13 is simply "Raganelli" and #15 is for S.C.A.R. today, in essentially the same location as it was as of 1964. There are several pages showing Karting Clubs and more. I will share the pagine bianche info privately.
My own research notes for Cesare Raganelli show:
Cesare Raganelli - Roma
# Alfa Romeo Chilometro Lanciato - Roma 28.4.46 2nd/ over 2000 supercharged
# Lancia Aprilia Coppa Gallenga 19.3.47 3rd/ 1500 Turismo
He raced an unidentified "Sport 1100" during 1947 at Pescara.
He raced a Cisitalia 202 (with Sergio Banti) on the combined Giro di Sicilia & Targa Florio race of 1948 but failed to finish.
Cesare shows up by name and dealership as selling two used Lancia Aurelia cars during 1955 and 1956 and there is the odd coincidence that each has the chassis number "1061". The 1955 sale was for a Lancia B50 and the 1956 sale was for a Lancia B52. I am sure there is much more that I've not tripped across in my studies.
A Roberto Raganelli of Roma (perhaps related?) was the purchaser of an early Giulietta Sprint Speciale during 1959 and also a 2600SZ during 1965.
I've not searched online as I am sure that you are doing so. One trick to remember is to place the last name first (i.e. "Raganelli Susanna") when trying a search as it sometimes yields slightly different results. And there is always searching the initial ("S. Raganelli") as well? One reference to Cesare Raganelli showed him as "Paganelli" instead and it may be that a thorough search should include such distractions if you find any sign of even one such erroneous reference to Susanna? For "Paganelli", you may learn a bit about a Napoli-based tuner and builder?
Good luck! John