Stephanie is the French feminine of Stephen — from the Greek stephanos (crown, garland). Stephanie Meyer (born 1973) — American author; the Twilight saga has sold over 160 million copies worldwide.
Stephanie 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 Stephanie reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.