When studying Chinese, I've often found that there are different ways to say the same thing, for example using a verb with a directional complement rather than a verb with resultative complement or a simple sentence structure.
I was told that the choice (prefering a directional complement over a base sentence structure) is due to a change in focus, thus with a directional complement the main event within the sentence is a movement taking place.
So, if I have these sentences:
1. 我妹妹到上海来了. [using the directional complement]
2. 我妹妹来上海了. [using the simple sentence structure]
3. 我妹妹来到上海. [using the resultative complement]
Are there any differences between these three sentences?
Also, I was told that the third one is wrong, but why exactly is it? Couldn't it be interpreted as a resultative complement where 来 is the main verb and 到 indicates the result of arriving at a place?