The with adds a nuance of a certain weary inevitability, as if the writer were in the relationship out of habit - i.e. without any real commitment.
However, the whole sentence is incomprehensible - I have no idea what you are trying to say: "Susan and I continue with the friendship two years later we met". It sounds like you were friends with someone you had not met.
It would have been very helpful if you had included some context and punctuation - it might have been understandable.