As others have asked, how do you know she was "mentally unknowingly blocking" you?
Sounds like a good excuse for an experiment - find out how far away can she be and still block you, and see if you can work out how far away she is when you can't see her.
I get concerned when people glom onto the first explanation for a problem which makes the situation someone else's fault.
Only when she was holding the rods and some of us were trying to turn them in her hands. Works ok with others. No mater how you twist what I have said I and other successfully dowse and have a large number of people who ask for our help. This seems to be new to so many, but it goes back centuries, just shows how this stuff is hidden from general knowledge. The above was only done for fun,but shows how dowsing can be interfered with.