Good advice here about resolving difficulties with a remote co-worker.

When it comes to delivering feedback, use the same formula that you would in any other feedback situation. First, provide crisp and clear observations of your teammate’s behavior as free of judgment and subjectivity as possible. (For example, instead of “you were rude to me,” try “when you interrupted me as I tried to be heard over the phone…”) Second, describe the impact of the person’s behavior. Phrase the impact as your reaction or impression, not as the objective truth. (“When you talked over me when I was on the conference call, I felt like you don’t respect what I have to say.”) Finally, ask an open-ended question that engages your teammate in a dialogue and helps you to understand one another’s perceptions. (“How did you perceive that call when you were in the meeting room?”) Don’t stop until you each have a clear vision for how a similar situation could play out better the next time.
Working remotely is great, but it can be an emotional rollercoaster.
Most of us avoid or delay uncomfortable conversations even with people who sit beside us. It’s natural to dislike confrontation. Now imagine how easy it is to let concerns fester when your teammate is two time zones away. Avoiding an important conversation is a bad idea with an office mate and an even worse idea with a virtual teammate. Get the issues out in the open as quickly as possible before they sour your relationship and affect your ability to get the job done.
Source: Harvard Business Review