I am so sorry that you are dealing with these family issues.
I have been there myself. I suppose "most" of us with chronic illness have.
You just have to "not care what anyone else thinks; whether they believe you are sick or not". I know one of my sisters feels that way and never includes me in anything because "I didn't figure you would feel like it anyway." Jab. Jab. I just don't care what she thinks anymore.
I hear people say, "Wow, you are looking great. I am so glad you are so much better." I always think if you could only see me without all of this health painted on and smile fixed in place but that's ok. I have said "Great. I am glad I don't look the way I feel." but then I gave that up and just say "Thank you".
Sometimes my daughter who lives away doesn't seem to understand why I don't travel more. I wish that were different. I hate for her to think I just don't want to.
I am like you and I push myself. Today I am really paying for spending 1 1/2 hrs. in the sun (a Lupus no-no) taking care of a neighbors flower/veggie garden and another hour helping my husband in the afternoon do our elderly next door neighbor's yard. Today I can barely move but it was so worth it.
I spent a full year in bed and I don't want to be there any more than I have to so I keep going because I am afraid if I quit, I will be quit.
Just hang in and live your life and remember you don't have to prove anything to your aunt or anyone else.

I suppose I ranted also.

Hugs and Blessings.
Possi