Witch hexes are supernatural abilities, and thus do not allow spell resistance, as a rule. However, the healing hex "acts as a cure light wounds spell" - and cure light wounds allows spell resistance. So does the healing hex allow SR or not?
The healing hex is listed as being a supernatural ability, so it does not allow for spell resistance.
Edit: It should be noted that not all witch hexes are supernatural some are extraordinary like cauldron and child scent.
Supernatural abilities never allow spell resistance regardless of whether they "act like a spell". If healing hex had been a spell-like ability, then spell resistance would have been in play.