Yeah, I've heard that somewhere else, too, that she didn't like first grave, so dug the 2nd. Because of that, I've kind of assumed she had no use for the 1st one, and either filled it in right away, or left it 1/2 dug and unused. I don't tend to think she haad plans to use the other one. In those woods, I'd think there would be tons of roots and rocks making digging fairly difficult, but not impossible, if you pick the right spot.
We had tons of rain in October. I did go walking in the woods a few times, though, as I live in the country and walk a lot. There are places you can get to easily, even when it's wet out, and places that are tougher to get to, or look as if they should be avoided, especially with slick, wet leaves on slopes and such. But if AB was familiar with those woods, and it appears she was (snuck off and spent the night in the woods??), then she would have known her way around better than strangers searching. It would be easy to throw some dead branches and a pile of leaves over the grave(s) to disguise them.