Do you have both open at the same time? Does it start another one up?
Anyway... Yes, the beta can "steal" attention away in ways, but I guess you're saying it can happen both ways.
I usually use Faststone to open pics and I don't have that problem, but I never run both at the same time either. The active PS will take the pic, but in FS you can also assign in which app it has to be opened. In Bridge, I don't know.