My sister won't have anything to do with me or our family?

[vipster1]

This has been an ongoing problem with my sister. I actually had it out with her last summer, because for every family event, she has had an excuse why she can't make it. She's sick, she has to work, blah blah blah. After listening to my mom for the umpteenth time about how my sis upsets her, I called her and asked her point blank if we did something to offend her, and why is she avoiding us? And the fact that mom is upset Well, that blew up in my face, I ended up being the bad guy, my sister saying that our mom should tell her if she's got a problem, not me. My mom is the type to not say anything because she doesn't want to rock the boat, but I can see it upsets her,. I also told my mom that I did my part with the phone call and look what happened, that SHE needs to talk to her. Now my mom is upset because she asked my sister if she and her boyfriend were coming over for Easter. She said no, they were going to the boyfriend's mom's - who lives not even 5 minutes away in the same town. They're not even going to stop by. Add to this that she has 2 beautiful nephews (my sons 2 and 3) that she hasn't seen since Xmas - and only because she had to. She really seems to have gotten worse after the birth of my 2 sons. She didn't even visit us in the hospital when I had my 2nd. When we had the big fallout last summer, she had her boyfriend call me back and he said whenever we get together it's always about those kids (meaning his nephews) and she feels like a 3rd wheel. NO ONE has ever tried to make her feel left out. Every time without fail, when we invite her over, she has one excuse or another. I've already tried talking to her and that got me/us nowhere. I just don't know what to do. I feel really bad for my mom - she just wants to have the family together and she's hurt that they are only going to be a few minutes away and can't be bothered to see her family. I'm also hurt that she has no interest in seeing her nephews, they ask about her when they see pictures, and I have to lie and say she's working so she can't see them. I could see if she were a good deal younger then me, chalking it up to immaturity and just not into the whole family/kids thing, but she just turned 40. I'm just hurt and angry. I don't know what I should do, if anything. Do I just wash my hands of it, tell my mom she needs to talk to her (which she'll never do). I just cannot for the life of me think of what we could have done to make her not want to see any of us. I tried talking to her and that got me nowhere