Sylvie is the French form of Sylvia — from the Latin silva, meaning "forest." Rhea Silvia in Roman mythology was the mother of Romulus and Remus.
Sylvie Vartan (born 1944), the French singer, is a notable bearer.
Sylvie 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 Sylvie reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.