They are individuals, no plant is exactly like the other. They look healthy though, so no need to be worried at all. There is a big difference between these two plants though.
Looking at your diary, it seems she isn't even in early flowering yet. At 16 hours of light per day, she might not be an autoflower.
Could be an explanation and you can just flip her into flower whenever you like.
Just give her some time and she might get even bigger than her sister and grow more buds. Good luck on your grow. ✊😇