I'm someone that isn't really social and social gatherings tend to be very tiring for me (this is at least partially due to the fact that I'm on the autism spectrum).
I have noticed that social gatherings at my aunt house are even worse because I'm expected to be social and present all day long, without the possibility to rest.
When I'm too tired, I tend to leave the table to go sit on the couch nearby. However, my aunt isn't very pleased about it and tend to find me some chores to do whenever I do that. Even if I lay on the couch, getting ready to take a nap, she will find me a chore to do. I tend to interpret that as if she was saying: "if you don't value our company, here are some chores you can do for us".
I don't mind helping around but doing the chores doesn't allow me to rest and I really need that rest. One time, I was so tired from being social for so long that I broke into tears the second I was finally home and able to rest.
As a result, I tend to avoid going at her home whenever I can (which hurts her feelings) and, when I come, I make sure to stay for a limited amount of time (I'm always the one asking to go when my parents and sisters won't mind staying a little longer).
How can I tell my aunt that I really need some time off without hurting her feelings?
Note and clarifications
When I see my aunt, it's always on a big social event (~10 people) and I don't really have the opportunity to have a one-on-one chat, except if I explicitly ask for it (which I have never done and it would be extremely weird for me to ask for). She does, however, phone me often.
Live far from my aunt and seeing her outside of those big social events would be too much tiring for me to do.
During the social gathering, I could choose to isolate myself in another room but I'm afraid that, without explanation, this would be seen as even ruder (since I would no longer be "with them").
My aunt knows that I have been diagnosed with autism but I'm pretty sure that she doesn't know exactly what it means and how it impacts my life. Also, the diagnose is really recent (only three months) and this was all very sudden for my family (except for my mum).
I'm a 23 years old, French woman.