What does her day look like and how long does she sleep when she has one nap?
I would guess all the NWs are OT or developmental since you've ruled out discomfort. Have you tried SEBT? Like 6pm? It doesn't work for everyone, but if your lo tacks on it can be a lifesaver keeping OT at bay. Even if they need one nap and two isn't working any more, it's still a big adjustment and OT can accumulate. We had a lot of 6pm bedtimes and long nights when she first went to one nap around 12 months.
We also had long (2-4hrs) NWs and it was horrendous! We went through a really rough patch of sleep around 14 months, and I'm still not exactly sure what it was but I honestly think the NWs were developmental rather than routine related because tweaking never changed them, and one week she just started sleeping through again, nothing we did differently. For about a month she would have these NWs probably 5 nights a week. It was awful. Sorry I don't have any advice on that, just sympathy! I was desperate to fix it and guessing OT, UT, teeth, etc. But really we just had to ride it out, and by the time it was over she was totally a toddler not a baby! Her receptive language was on a whole new level, she was running instead of walking, and just older all of a sudden. But the point is, it did end.
Hope you all get some sleep soon!