Who is more generous? Is Michael selfish? Should Skye just get over it?

Michael and Skye work together. Skye often purchases can's of coke for Michael from the staff vending machine at her own cost, despite the fact that Michael earns a significant amount more than Skye. Occasionally, Michael will bring in a can of coke from home, but will not considr bringing an extra can for Skye who as mentioned is quite generous with the provision of coke for Michael.

Michael brought a can in once for Skye, although Skye was sick that day so didn't feel like drinking it. Plus it was caffeine free diet coke and she wasn't too keen on it.

Michael now thinks that this one occasion of being thoughtful makes up for all the times Skye has been thoughtful. Obviously Skye disagree's.

Does Skye have the right to be so perturbed? Is Michael the selfish fiend Skye believes him to be?