If, as we all are supposed to think,
a) female aikido is NOT different from male aikido at an advanced level
b) strength does not make a difference,
Anyone who thinks strength doesn't make a difference needs to train with stronger people.
At equal skill levels, the stronger person will win. That's just physics.
With that said, some of the most intimidating people I know in aikido are small women. They make up for their diminutive size with tremendous skill and enormous spirit. Small women absolutely can develop excellent aikido.
But so can men. Which is why competitions are and should be segregated. Judo has weight classes, too, for the same reason.