Ive never read anything to suggest she was pushed or asked to leave. From the little I have read I think it had something to do with her husband, who is American, needing to go back to the US and her having to go with him.
That would make sense. And I think Peri leaving (and the manner of her leaving) did leave a slightly unsettled feeling which didn't help integrate Mel within the show. You had Peri suffering some horrid experiment and then .. Wallop! Next week Bonnie Langford is skipping around the show - with no real explanation. A proper story to give her background and texture would have really helped.
