Joe Lucky --
A suggestion -- you can be agreeable to the suggestions about cards and contact for holidays, in person, but I would set up a family facebook account SPECIFICALLY to send congratulatory notes to your sister (and family) on the holidays... and stick to paper cards for Christmas, birthday and graduation only, with or without money... Post the occasional family photo to this facebook account, and look like you are actively interested in their posts with a few likes and comments. It is amazing how little effort it takes to make everyone feel like you are connecting, and only you will realize how superficial that is. If they are not yet on facebook, then get them on, referring back to the thanksgiving conversation about connecting with family more...
As others suggested, I would just keep inviting (maybe via facebook for all to see?) your sister to visit you.. e.g., "congrats on those valentine's day cookies you made... do you want to come visit us to celebrate St. Patricks day on Tuesday next week?" ad nauseum, and using invitations for awkward dates and non statuary holidays.
In fact, that may be all that they want...
MMM1970
"My mother divorced my dad when I was a teen, and she had angst about it. She was very often "revising history" in her head because she wanted things to be FAIR. I didn't care about fair.
.....
But man, later in life she talked about how she paid a certain amount for my wedding, the same as my sister and brother. And she didn't. "
I can truly relate to this, (in fact, specifically about the wedding... in my case, the in laws were remembering what someone NOT them gave us towards wedding costs, and thought that was what they gave.. to justify paying for SIL's much more expensive wedding in full) and realize it is just human nature. I finally asked the person(s) doing this to just stop talking about it, and put their money wherever they like, because it made me upset over details and I truly did not care (as much) about the money as about time spent together... fifteen years later and that made a huge difference in our relationship.