I guess what was missing was the urgency of the performance, and the juxtoposition of the fact that Peeta once saved her life by throwing her intentionally burnt bread. They kind of glossed over the bread thing, and barely even indicated that Peeta risked his own ass to get a loaf of bread to her. This was partially lost because the movie didn't really convey how starved District 12 was; in the beginning, we see a singular scene of a scrubby old dude gnawing on some bones, but that doesn't really indicate that they're starving, especially considering Katniss, Gale, Prim, the mother, and... everyone else in District 12, looks kind of dirty, but not starved. Poor, but not destitute. So the scenes of the rain and the bread just look like Peeta threw a sleepy Katniss a loaf of burnt bread, and we were given one or two lines about how Katniss remembered it.
So what comes off, is Peeta making some play about pretending to be in love with Katniss to garner support, Katniss kind of figures it out and gets on board, and then puts on a mild act to go along with it and help him out. I wasn't under the impression that she was conflicted about it, just that she's a decent person who wants to see the fewest lives lost and saw her semi-buddy hurt, so helped him. I mean, she only kills defensively. Her being conflicted about Peeta though is something pretty tricky to convey over the scope of the film, short of showing, perhaps, twinges of jealousy in the right circumstance. But I dunno, I didn't even feel like Peeta assuredly had feelings for her.