Need help with adult daughter and her interaction with the family.
We have three daughters - 30, 27, 24. In general, we get along very well and love each other very much. The 30-year-old daughter is married and lives 4 hours away (let's call her Martha and husband Jim). She is very intelligent and very successful professionally and financially. The other two get along with each other extremely well and have a mutual respect for each other and for my husband and me. They both struggle with their relationship with Martha.
Here's my issue: Jim loves Martha very much, but seems to be indifferent toward us. That's not to say he hates us, but he's indifferent to us as with most people, including his own family, except his sister, and his friends (guys since high school) that he's very devoted to. When Jim and Martha come, he does nothing. Sits all day long, listens to audio books, and plays games on his phone and barely interacts. Doesn't thank us for our hospitality, Christmas gifts, for cooking great meals, nothing. I say "Good morning," he says "Greetings." Never asks about how we are (both cancer survivors), never asks if there's anything he can do.
Martha loves Jim very much. We do not criticize or speak badly about Jim at all - she loves him so we are polite and warm and cordial. Martha also never lifts a finger, thanks us only sometimes, but is generally grumpy. She makes snarky remarks - Jane put something of Martha's in the room they sleep in (the room they always sleep in that has a bathing suit in the drawer and crocs in the closet for her) and said, "Martha, it's in your room." Martha spit back, "That's not my room"
, disses her youngest sister constantly, makes crappy remarks about the food available ("I don't like chili with meat." "I hate ham." "I don't like apple strudel" but brings no food, takes part in none of the planning, cooking, or preparations.
This is the tip of the iceberg. There are so many snarky, nasty little things that she says, and it breaks my heart We gave each of our daughters a sum of money, then gave each a smaller sum on a staggered scale (to the one who needed it the most to the next, and then Martha) and told them why we were doing it this way over the course of a few months, and she said to one of her sisters, "I probably won't get any more money."
?????
When she was a girl, up until the middle of high school, she was a warm, caring, wonderful person. Things changed, and she's become hardened and dismissive - doesn't answer her phone when we call, doesn't answer texts, barely communicates unless she has good news from work to share.
I love all our children, and this breaks my heart - that she's become this uncaring, nasty person, that she is rude to her sisters, and that it affects our family harmony and I'm mourning the loss of this once lovely person. I've been struggling trying to decide if and how to bring this up. My first inclination is to separate myself a bit - don't call, take my time answering her texts and calls when they do occur - but I don't know if I'm doing that to be bitchy or just what my purpose would be. My husband suggested we talk to her on a visit, face to face. I wouldn't start by saying, "Why are you such a shit to us?" but wonder where to start?
= new reply since forum marked as read
She's taking medication for both. It runs in our family - I've just weaned off mine and am doing fine.
I appreciate the other responses as well. I don't think it's marital problems. I'm seriously reading and thinking about what you've all said and very much appreciate each of you who've taken the time to read and respond. 
Response to phylny (Original post)