Your lucky Lottie, synulox 'palatable' and none of my normal cats will eat them, only Taz.
I dont think a pill gun would be much use in this case as BC cant handle Mary.
What is she being treated for? Theres a long acting AB available it only helps for some things and its debatable as to how effective it is. Its called Convenia if you wish to ask your vet about it.
Only other thing i can think of is to get a tin of puree food form your vet called a/d and crush the tablet really finely into a tiny blob and syringe it in her mouth/smear over her leg. It will mean you need to catch her but needs must.