Though given how other New Democratic Parties have been faring across the country lately, I can't say she's as "not up to the job" as it appears--she did hold *a* base last year, though it unfortunately didn't include the 416.
Maybe the more proper question to be asking esp. following the federal debacle is whether the *party itself* is, any longer, up to the job.
Maybe.
I think she and the party had a golden opportunity (tired and scandal-plagued Liberals, Tories who were shooting themselves in the foot), and they blew it. That their seat total remained the same is a silver lining, but shouldn't be seen as any kind of victory. They took seats which will likely be in play in future elections, and lost what were once safe NDP ridings. They had no message, no vision, no compelling alternative to what the Liberals were offering, and no real explanation for having forced an election that the electorate largely didn't want.
I think it was a Horwath/Ontario NDP failure. But you have a point. There is a malaise, for a lack of a better word, in the NDP as a whole. They are so close to ditching the third party label, and becoming seen as a valid governing party, yet they do not quite know how to get over that finish line. I think Notley was more of a fluke than anything else, but nonetheless Alberta is a great opportunity for them, and they don't quite know what to do with it.
As for the federal debacle, the general "wisdom" appears to be that they shifted too far to the centre (they let the Liberals outflank them on the left) and/or they were simply victims of the Anybody-But-Harper movement which went Liberal as Trudeau had the momentum. I think both theories are bunk, and they will be in trouble if the party tries to rebuild by believing either or both theories (just as I think the Tories will screw themselves over if they explain away their loss mainly on Kory Teneycke's Harper Derangement Syndrome explanation). I think they foolishly underestimated the Liberals, and unlike Trudeau, didn't have a compelling message. They basically did the same thing that the Liberals did vis-a-vis Harper under Dion and Ignatieff -- they simply assumed that the electorate was as contemptuous of Harper as they were and would simply wake up and realize that the Liberals were the natural governing party. In this election, the NDP believed its own biases -- the voters found Trudeau as lacking as they did, and the Liberal platform had no legs. We're the NDP, we did so well in Question Period, we're the real alternative, we shouldn't have to sell you, trust us.
In some ways, the NDP seems to be making the same mistake again and again. Which goes to your point about the party itself.