My boyfriend and I are in our early 20's. We've been together about three years, and we have lived together for most of that time. We both work, and our hours are a little crazy. Many days we only get to spend 2-3 hours together because of our different schedules. His sister, who is two years younger than him, lives a few hours away from us and we only get to see her about once a month or so. I do really like her and consider her a friend, and we have a lot of fun together when we hang out. But lately, she's started doing this thing where she calls every day, at least once (but sometimes multiple times) and wants to talk to him for hours. We used to live only ten minutes from her, and during that time she didn't even talk to either of us. We both got new jobs and had to move last year, and for the past few months she seems to be starved for his attention.
I really have no problem with him talking to her, because I know they miss each other and I know how it feels to live away from your family. It's just how often she calls, and how long she wants to talk to him for. A lot of times our plans are interrupted because she wants to talk to him, and she tends to get offended when he tells her he's busy (which he has started doing a lot more often). She'll call when we're having dinner, really late at night, or when we're out doing something together. She called the other day when we were in the middle of cleaning the house, and got all upset that I was talking to him in the background. He had told her we were busy but that he could still talk, so you'd think she'd understand that he wouldn't be giving her 100% of his attention. Apparently she made some comment about me being greedy and taking up all his time. I really don't think I am, but when she calls multiple times a day, chances are she's going to call when we're spending time together at least once... so that's probably why she has that impression. It actually kind of hurt my feelings that she would say that, but I can't confront her about it or anything since I'm technically not supposed to know she said that.
Does anyone have any tips on how I can deal with the sister situation without upsetting anyone?