Here's a brief narrative, pieced together from several eyewitness accounts. (The first batch of photos are by Steven.)
Hawk watchers spotted who they presumed to be Christo in the nest that he has been fortifying for Dora. However, it turned out to be an intruder, another red-tailed hawk who was unfamiliar to the Park regulars. (The other hawk wasn't Barucha/Nora/Not-Dora.)
That's when the fight started. One eyewitness said that the intruding hawk was the aggressor...


By all accounts, Dora, on top in the above photos, kicked the intruder's ass (paraphrasing). The intruder fled. Red-tailed hawks are very territorial, and the sight of an intruder in her nest, where there may be eggs, likely angered Dora.
After the skirmish, Dora struggled to take off ... Ranger Rob (aka Rob Mastrianni, a Manhattan Ranger supervisor and East Village resident) was eventually summoned to the Park. He thought that Dora would be fine, especially as she started to fly.

She eventually made it into a tree, where Christo brought her a rat...

... and later in the day, Dora appeared to be doing OK...

And a few other photos of Dora today ... via Ryan John Lee...


... and from Garrett Rosso...

H/T Emma Haddad!