Audrey ('noble strength'), Bridget ('exalted, strong'), Valentina (from valeo, 'to be strong'), Gabriela ('God is my strength'), and Matilda ('mighty in battle') all belong here. The cluster runs from classic to modern.
Strong without being heavy
The most successful strong-girl names pair strength-meaning with soft sound. Audrey is a good example: the meaning is 'noble strength', but the name itself is all gentleness. Parents who want backbone without hardness tend to lean this way.