Yeah I've thought this before, the type of place she went to at the beginning would probably be less haunted than most places because exorcists go there all the damn time.
The way I see it most of the exorcists could be hacks and it would still work as long as a) some of them are for real and b) the effect of exorcisms/cleansings is at least a little bit cumulative.Depends on if the exorcists also have legit powers too , just b/c you study and perform a cleansing ritual doesn't mean it'll work