Personally in the situation described I would use a roll to activate
the ability and then only use rolls if she is doing something
significant or different with the feat. I get the impression that
there was no immediate reason to vacate the tree and no weird magic
trees involved, so I don't think that another roll would be needed.
As for the hunter, I would probably allow him to have running at 13
for 1HP (p58) there and then - it is mundane enough and reasonable
that he could have it. But he can't use an affinity as an active
ability (p118).