Splitting up covered more ground, but without any idea of coordination, all it would lead to is disorganized chaos- and all of this showed plainly in Gretel's expression. It agreed plainly with Amy's words and tone, even if she had no idea what in the world kind of experiences these two have had together. From the sound of it, they'd been down this road before, and apparently it never went well.
So... perhaps they were dealing with someone with a memory problem. Or a learning disability. Either way, she wasn't thrilled, and stood in a dubious silence waiting beside Sam for the two of them to hopefully come to a conclusion.