I have a SOMEHWAT similar story... maybe it will help.
My ex ADORES her parents and treats them like gold. I think that is WONDERFUL. But... her father has become ill and needs a lot of care. That allowed very LITTLE time for me. I TRULY did not mind... but I didn't fit into the equation. It was family, work, school, more family and then I fit in somewhere down the list. Anytime spent with me was time she COULD have been with her Dad and she felt guilty. She started basically ignoring me because she was exhausted and THAT'S what angered me and triggered an argument that lead to the end.
Now, when her father dies (and I pray not anytime soon) if I had been around she would have blamed me for taking away precious time with her Dad. Now she's got all the time she wants.