If she had a cell phone there is a free app called Life 360. It is very accurate. We have it on all of our phones and I actually used it to find my cell phone out on the soccer field one day. My husband was able to pull my phone's location up on Life 360 and told me the phone should be beside the soccer goal and it was! I suggest this possibility because again, it is a free app and could be added to most phones.
Along these same lines, if she is deceased, I would want to know where the local Amish community dispose of deceased farm animals...cattle, horses, stillborn calves, etc. If there is a burial area or a general area where this occurs, they need to look carefully. It would be a good area to conceal a person and could possibly throw off cadaver dogs trying to track scent.
It is weird how they are concentrating on creek areas. I live near the Honey Brook area where they were asking property owners' for permission to search. It is an area along the East Branch Brandywine Creek.