Justina is the Latin feminine of Justinus — from iustus, meaning "just" or "righteous." Saint Justina of Padua was a 4th-century Christian martyr.
Justina is widely used in Spain, Italy, and Portugal.
Justina 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 Justina reduce to 4, The Builder. This is a traditional interpretive system, not a factual claim about the name.