I used to have kitties, but now have 'the dog for people who like cats," basenjis.
They ARE very catlike in their demeanor.
I have one that's a little shy, but I've noticed, they respect their established hieracrchy, and are easier to live with when we do too. A lot tof times her behaviors come acrooss as shy, but if you really look, she's just doing what the higher ups have signaled she do.
Eating, she waits, petting she waits, getting nails trimmed, SHE can go first LOL
I've never had more than one cat, so maybe cats are the same way? Is she getting a signal from the other to hold back?
The way we've dealt with this is to always involve the shier one in the petting, or attention of any kind. The alpha learns that it's ok to pay attention to both, the shyer one learns, "Hey, alpha says it's ok, I like it!"