Faustina is the Latin feminine of Faustus — meaning "fortunate" or "lucky." Empress Faustina the Elder (c. 100-141 CE) was the wife of Emperor Antoninus Pius; Faustina the Younger (130-175 CE) was the wife of Marcus Aurelius.
Faustina does not currently appear in the US Social Security Administration's top 1,000 girls' names, so we don't publish a US rank or birth count for it. That says nothing about the name's standing elsewhere in the world — only that it sits outside the ranked US data we rely on.
In Pythagorean numerology the letters of Faustina reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.