Wambui is from the Kikuyu Wambũi — one of the nine daughters of Mumbi (the ancestral mother of all Kikuyu clans). Wambui Bahati — American actress and activist. Wambui Njoroge — modern Kenyan figure. Wangari Maathai (1940-2011) — full name Wangari Muta Maathai — though not exactly Wambui, was the first African woman to win the Nobel Peace Prize (2004); founded the Green Belt Movement (1977) — planted over 51 million trees in Kenya; her movement is to global environmental justice movements; her family naming tradition includes Wambui-family heritage.
Wambui 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 Wambui reduce to 6, The Nurturer. This is a traditional interpretive system, not a factual claim about the name.