Bristol, to use an old-fashioned term, is a twerp; her statement is unlikely to have legs. Your analysis of Palin's and conservatism's loss is accurate, I fear.
Bristol’s comments will have legs with the subset of Conservatives who are very supportive of Cruz and are aware of it.
These are people that the eventual nominee can’t afford to lose. They, like the core supporters of all the candidates, are the ones who will in all weather go door to door canvassing in the Fall, work phone banks, spend election day driving people to the polls.
They’ll remember this, to the point of ignoring their own candidates exhortions to get out and work for the nominee, should it be someone other than himself. They aren’t the kind of people who you can alienate and still expect to have good retail politics and a winning GOTV ground game.