Wilhelmine is the German form of Wilhelmina — from the Germanic wil (will) + helm (helmet, protection). Princess Wilhelmine — multiple historic German naming.
Wilhelmine 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 Wilhelmine reduce to 2, The Peacemaker. This is a traditional interpretive system, not a factual claim about the name.