Karla is the Spanish, German, and Czech form of Carla — the feminine of Karl/Carl ("free man" in Old Germanic). Karla Bonoff (born 1951) — American singer-songwriter. Karla María — Mexican-American singer.
Karla 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 Karla reduce to 7, The Seeker. This is a traditional interpretive system, not a factual claim about the name.