Continuity mistake: When they are back in the cemetery at the end, the Angel shows up right behind Rory. In the first shot facing Rory, as the camera zooms in on a close-up of the Angel, the Angel's right arm/hand is pointing straight out, and its left open hand is up in a grabbing position. After River asks where the hell it came from, in the Angel's next close-up and all subsequent close-ups, its arm/hand positions are reversed - left hand is pointing straight out and its right hand is up. Yet in every shot of the Doctor, River and Amy together, in the foreground we see the Angel's left hand is up in the grabbing position.
Picture added by Super Grover