Is there a history of her feeling stressed toward your family?
Yes. To be more specific, she had some issues with my aunt's husband (I called him uncle in the previous posts) because he started to notice behavioral issues with my wife. For example, one day (October 2012) my W and I were at my aunt's house. Earlier that day my W told me that she wanted to go to the pharmacy after leaving my aunt's house. While we were at my aunt's, my uncle-by-marriage was talking to me about some remedies for a problem that my W was having. He then wanted to go to the pharmacy with me to show me the supplement that will help with my W's problem. He also needed to buy some supplements. But before I left I spoke with my wife (back then we were still dating) and let her know that we were going to get something for her really quick. She then got upset and said "But why are you going now? I told you I wanted to go with you after we r done here!." So I told her that we were still going after we leave the house as she asked me to, but that my uncle also needed to get something for himself. She then started to raise her voice and got really upset; "I told you before that I wanted to go with you!..You never listen to me!" This happened in the middle of my aunt's kitchen, where both my uncle and aunt were standing, as well as my cousin and his wife, and my younger cousin. My cousin's wife tried to speak to her so she can calm down (they know each other since before we met). I told my uncle that I will just stay at the house with her, but then my W decided to come with us. She had an attitude from the moment we got in the car, to the moment we arrived to the pharmacy, and pretty much all night. Later on she told me that the reason why she wanted to go just with me is because she needed to buy personal items (girl stuff). But she never told me that before, and I also asked her what she needed to buy and I will buy it for her. So at that point I understood her frustration, but my uncle wasn't too happy with the fact of two people arguing in his house. That was just one incident. Similar incidents happened earlier and later on.
And yes, I may not know how she feels, but that is why I supported her during those "attacks".