I think maybe your shy pig is bonded with your hubby, so you need to bond her to you. Take an old blanket & have a nose to nose floor time with her... start out floor time while using a "piggy-pen" but sit / lay (if your pen is big enough) in with your
GPs (hence nose to nose). Main thing is to have them get use to you.
Besides regular daily floor time with my
GPs (where mine roam free), I do individual bonding time at night with my
GPs where each will have to have lap time with me watching
GP you tubes (I usually have multiple tabs open to switch between other tasks). I repeat playing the same videos till they are comfy then switch to other
GP you tubes. Having their fav. treats close at hand is very important (you want to give them a treat as soon as you hold them).
I think you'll need to spend more time playing with your
GPs because they could be bored (even with each other).
As to the trashing the cage & taking down the walls of the cage... what do you use to hold the walls together? If zip ties do not work (if they chew on it but as far as I know zip ties are great to secure C&C b/c the
GPs rarely touch them)... maybe use some metal folder/report clips?
Hope this helps.
GPs are like little humans, they are loving attention from us.