Sancha is the Spanish feminine of Sancho — from Latin sanctus (holy). Sancha of León (1018-1067) was the Queen of León whose marriage to Ferdinand I united Castile and León — mother of Alfonso VI and Urraca of Zamora.
Used widely in medieval Iberia.
Sancha 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 Sancha reduce to 1, The Leader. This is a traditional interpretive system, not a factual claim about the name.