I'm interested what makes you think that? Obviously, the clues are there with the farewell notes, empty packet of pills and alcohol. However, she might have been creating a false trail and faking her own suicide. The letters would still have emotional significance as she was cutting ties and starting again. The area was searched thoroughly, and it's popular with ramblers and cyclists. It's strange that her body would've evaded discovery for so long but it does happen.
I'd like to see the CCTV footage again to judge if the girl in the newsagent's bares any resemblance to Ruth. It's coincidental that it was on the first anniversary of her disappearance and she was preoccupied with the newspapers that day. From the stills, the girl has quite short cropped hair, which Ruth might have adopted to hide her identity.
No, this is nothing else other than a feeling, nothing to substantiate it as such and as I said it is just as likely that she had made plans to change her life for some time before she left for good.
As Alb1on also points out, the amount of human traffic that has been in that area since would diminish the chances of remains not being found.
I would, however, dispute that the initial search conducted was thorough, and my reasoning for that is only that one of the officers involved went on public record to say that he did not believe that either. (Think that he was the Family Liaison Officer for the Wilsons).
This, put together with a young girl completely being able to so successfully disappear off the grid - no financial traces, no medical needs, just gives me some doubt, that's all.
I have to be honest and say that even living this close to the area, I can not recall hearing about this case at the time (maybe I had other things on my mind!), but I think that it goes to show that the publicity of the event was perhaps lacking, on the part of the authorities/press. Indeed, more is written about it today than at the time.
On the subject of the newsagents CCTV, good luck with finding that - I can now only find the still frame taken from the video and it could be anyone, male or female. I note that just over a year after she went missing, a newspaper article stated that the Wilsons had spent much time poring over the video and gradually came to believe that it was her. So even they were not certain. Be useful to watch it again though.
MOO