Christa is the Germanic short form of Christina — from the Greek christianos (follower of Christ). Her motto: "I touch the future. Christa Wolf (1929-2011) — German novelist; Cassandra (1983).
Christa 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 Christa reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.