It is 13. From the marriage processetti (images 349-360 starting here) you can see on her birth record she was born 4 Mar 1841 (original here).
In the Kingdom of Two Sicilies (1816-1861), a male had to be at least 14 and a female at least 12 to marry. Males under 25 and females under 21 also needed parental consent. (Cod. Leggi Civ., Lib I - Delle Persone -, Tit V, Cap I, Art 152, 163)
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