I actually like the ontological whirlwind of Donna. I think her uncertainty gives her a grace under fire that really grounds the team. She takes things in calm, collected strides.
With no place to live and her powers being drained she just carries on.
“Who is Donna Troy” was the star of the pack, for me. You get to see some nice growth from Dick, in addition to flushing out some of Donna’s “history”.
Does he see Donna as a friend; or maybe he harbors something a little deeper for her? They go way back, obviously. Donna was there for just about ever first and big moment in Dick’s life. I think that is it. Donna is the one woman in Dick’s life who has and will always be there for him, no question. I think he starts to realize that that kind of love is so much more. Either way she definitely distracts him from Kory, which is not hard to do. 
But I have to agree with Dick. Why is Donna marrying Gordon Lightfoot; and why is he calling himself Terry? It will always be Donna and Roy for me.