Translation:The friend is to their right side.
I don't know what the hypothetical context of this sentence is, but it is weird. Maybe there's a group of four people and the two in the middle are an enemy of one and a friend of the other. Meanwhile, another two people are spying on the group of three people, and one of the spies is explaining who is who to their spying partner. "Sharon is an enemy, and Karen is a friend, and those are our targets Jason and Murray in the middle. The friend is to their right side."
I answered 'The friend is AT their right side'. Is there a different translation for that? A quick search says that TO is a preposition of movement. Also checked Pleco, 在 can a verb which means 'be at, in, or on (a place).' Can anyone verify what is correct. Reporting it anyway.
This sentence translation is not consistent with the previous sentence (the dog was to left of the doctor. There is a difference in English between something being to the left or being to someone else's left. (Unless we are viewing someone from behind, we would distinguish between our left and theirs; this is quite common, such as on a stage). The dog is to the left of the doctor. The dog is to the doctor's left. The friend is to the left of them. The friend is to their left. What would a Chinese person say in order to make this distinction grammatically? Or do they?