I have read in grammar books that a comma is usually used when making a complex sentence. For instance:
If you keep talking to your mother like that, I will have to teach you manners.
Although she is smart, I won't give her the job.
On the other hand, I have also read that a comma is not needed when the independent clause comes first except when the dependent clause is a "non-defining clause". So,
She likes soap operas, which I find boring.
They finished the job on time, which they rarely do.
That house,which is for sale, belongs to a German family.
I won't let you go to any parties anymore if you keep telling me lies.
She is really shy whereas her sister is really talkative.
I made up the above sentences, so they may sound not really natural or even wrong in terms of meaning, but the grammar aspect is my goal here.
Last but not least, I wrote the following sentence:
- I'm willing to help her although she has always been very rude to me.
But somebody corrected it like this:
- I'm willing to help her, although she has always been very rude to me.
I thought that a comma was not needed when the independent clause appears first. (Except the non-defining clause case)