LO wakes up at 5am crying / screaming (EVERY DAY)

Is anyone going through the same? My girl is 21 months old, sleeps through the night (usually 7p-7a) but it’s been weeks since she started waking up at 5am — RELIGIOUSLY — crying / screaming, but not wanting to wake up. We have to go there, calm her down and most of the time we pick her up and rock her so she can feel safer, better, etc. What the heck!!! Nightmare? Growing? Scared? Is this developmental? Ugh. She goes to daycare everyday (and loves it)! She’s been going since November, so not sure.