It has been used as an independent name since the 18th century.
Annie was massively popular in the late 19th century, faded, and has returned in the 2020s. Today it sits in the U.S.
Annie 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 Annie reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.