This sentence seems a poorly constructed translation of the English phrase, “Once burned, twice shy.” Why is “scottata” in feminine singular and why is the verb “fare” either in 2nd singular indicative or 2nd singular imperative? Is there a reason for this that I don’t see?Shouldn’t the whole construction be impersonal? (“Una volta si scotta, la seconda volta si fa più attenzione.” or better yet, “Una volta bruciati, due volte timidi.”)
I do not think it is poorly constructed.
If you understand the first part as an ellipsis of the auxilliary verb for the perfect parallelism, then in Italian you have the choice to use the male or female form, and the female form here simply sounds better.