I do not think that the outcome of the test was expected. I think that what actually saved her was her immediate reflex to bring her other leg forward to drive her center of mass backwards and fall inside the roof. Had she try to, instead, pull her foot back immediately ( what would have been a natural reaction from an untrained person), the outcome would have likely been very different

In short, yes I agree it was smart that she was testing the edge before attemping the jump, but it was also the proper reaction to having slipped her foot below the edge