If she'd heard a Paisley accent in her youth, and found it distinctive, chances are she'd recognise it if she heard it again.
I'm from Leeds, but haven't lived there for a number of years. I can still spot a Leeds accent when I hear it, either a west Leeds accent, or a south Leeds accent, which is very different, as well as a Bradford accent, which is distinctly different, while most southern folk can't distinguish even between a Yorkshire and Lancashire accent.
So I'm inclined to accept Amy recognising a Paisley accent, even if it's been a while since she last heard one.
I wonder how many viewers will write to the BBC complaining about Moffat trying to pass off a blatantly Partick accent as Paisley...