Hi R.,
Your daughter reminds me of a sister of mine and a little of myself.
When I read your post I felt a lot of sympathy for your daughter because of the "pressure" a sensitive person may often times feel to perform to the expectations of others despite inner promptings from one's own individual self. I think you're a caring parent who wants the best for your child and it is obvious you want her to be well-adjusted. I will share some of my insights with you because I think maybe it could ease your mind a little about your daughter's occasional reactions to social stress.
In my world, as I experience life, my instinct and intuition seem often turned to a high-to-medium perception rate that seems automatically adjusted by someone's "vibes" or feelings whether it's "theirs" or even if it's just "stuff" the adult is carrying around or is surrounded by. Put that on top of whatever I am dealing with personally at that moment and the equation can get really tricky.
Adults live in a highly-charged atmosphere rich with pressures and tensions that we become masters of disguising or denying. Some kids can't handle it; and it's not healthy to expect this from them. Especially when they are drummed with the truthful and honest message. "How truthful should one be?" might be a question in a child's mind that they are not always able to even articulate within themselves.
If an aunt comes over and she's hiding that she's worried about getting laid off and is full of tension and worry and somehow your daughter is picking up on that and doesn't feel strong enough to handle her aunts emotions whether intellectually, emotionally, etc., please don't force her. Give your daughter time to adjust and discover her own coping strategies for those situations. Take time to observe her reactions, try to "read" her body cues without latching onto the obvious and then after Aunt Hilga leaves, have a loving, gentle, and understanding conversation with her so she can feel "safe" in those situations with you there to guide her. When you open up to her, she will have a good role model to follow.
As an adult, when my inner emotional landscape is sensing overload from some source and I know I can't handle it, I politely make my excuses (sometimes not)and give them some space. It would be abusive to myself to force myself to take emotional responsibility for someone when I sense that I am out of my depth. Sometimes I need to take a step at a time instead of taking on way too much, too soon and when I am not ready. I have discovered, (sometimes the hard way) that a healthy response for me is to listen to my inner guidance and go from there at a pace I am able to manage wisely.
My parents often forced me into a "normal" expectation mold, whatever that means. Maybe they were successful to a degree, but I found I had to deal with an ugly mess later trying to "grow up" with so many of their unfair and unreasonable expectations jammed into my psyche often willy-nilly and helter-skelter, and I still have to deal with a certain amount of fallout in my life from their lack of perception or unwillingness to perceive my sense of responsibility towards myself as a human being. They had difficulty respecting me as a person because they could only see me as a child; and later, as an adult, I had an exponential growth of difficulties all relating to issues essentially stemming from the quality of respect I was shown as a person and human being, especially that from my parents.
Take any average person off the street and give them 150 lbs. to lift and you'll find some people for whom it's not a problem and others who could not lift it at all. Maybe this could be how your daughter feels sometimes when she's expected to respond in a certain way under certain social circumstances.
Anyway that's my advice and insight. I hope it's helpful to you and your daughter.
-M