the idea in having identical hides is that they don't feel they need to choose their favorite for security over their need to regulate. it's just another way to reduce any unnecessary stressors.
your snake choosing one over the others is just your snake's preference, that doesn't mean it's not secluded enough for her, it's that she doesn't like the others.
two identical hides is a tried and tested method for keeping balls happy; whether you believe it or not is up to you.
Thanks for the tip, it is a reasonable explanation and I will change them for identical hides, honestly when I bought them I was thinking more on the aesthetics rather than the stress factor.