I had a similar situation where a neighbor at the lake brought his Jack Russell.  Said she was very friendly and did not feel threatened.  I am a very over protective mom and did not take my eyes off of her.  My husband had Sophie on a leash.  The minuet I saw her teeth show I hauled Sophie up so fast I was beside my self all day thinking I may have hurt her.  Thank god she wears a harness.  The only other option guaranteed would have been death or al lot of surgery as she was going for her neck.  All is well but I do not trust what other people say about their dogs being good.  Make you wonder their judgment!
 