Yes, teenagers typically are not diagnosed with personality disorders, as brain development continues well into the twenties, and often what seems like a disorder in the teens might disappear with maturity. However that mental health professionals have thought she might be afflicted with BPD is telling.
What is typical is that BPD symptoms become more noticeable when relationships deepen. The people who have the closest intimacy with individuals with BPD (family members, close friends, lovers) are the ones who usually observe more of the problematic behaviors.
That you are asking if you “should have to stay in this relationship” is a

and you are wise to question if this is healthy for you long term.