She lost her own riding, but her party still won the most seats so it is common when a leader loses their seat but party wins to run elsewhere as Don Getty did in 1989 and Clyde Wells did in 1993.  Donald Trump lost his own state (New York), but he is still president.  Likewise if her party wins fewer seats than the NDP, she will be gone as premier even if she wins her own riding (which she likely will as its one of the safest BC Liberal ridings in the province).