Justa is the Latin feminine of Justus — "just, righteous." Saint Justa (3rd c.) was the elder Christian twin-sister of Rufina — together the patron saints of Seville and Spanish potters, martyred for refusing to sell their wares for pagan rituals.
Featured in paintings by Murillo.
Justa 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 Justa reduce to 8, The Visionary. This is a traditional interpretive system, not a factual claim about the name.