Unfortunately it is really hard to say whether the runny bum that is maintained is the result of the AB (my hunch is that it isn't) or whether there is something else still going on (much more likely in my opinion). Going twice a day and still being runny is not good. So, I would take her back to the vet for some more tests.

I am sure your vet will know what the powder is. However, prokolin might be preferred in a situation like yours where the stool is still loose as it contains a bulking agent. See what your vet suggests.

Good luck and please keep us updated