Well, my dear Samawick - it is terribly obvious just how painfully insecure, awfully frightened & desperately this woman is. She is trying to "own" your brother totally! Which, IF she's not careful, her very own behaviors will cost her the love & devotion of your brother. After all, a person can only tolerate a certain amount of that type of "smothering" and obsessive compulsive jealousy of others. I too feel that your attendance at university near your brother is a good idea & I'm SO very glad to hear that your brother does not cater to his wife's crazy whims & wishes - in NOT wanting you to be there.. It will be great for him to have some of his family with him, near him - there is nothing quite like that sense of connectedness, feelings of trust & sense of comfort it affords having at least one relative nearby. Particularly when he is being bombarded so strongly with such insecure nonsense & fears & she is not likely to stop unless he can put a stop to her. Many times you see how one spouse (like your sister-in-law) tries to get her husband as far away, separated & alienated from his entire family in any way possible; it is just part of a sick, disturbed relationship scenario. Needless to say, she would benefit TONS from alot of mental health counseling but people like her rarely see THEIR problem, they are just SO good at seeing everybody else's. (LOL)
I believe if you can step back & look at the BIG picture here it will help to keep your ego or your "hurt feelings" response to your sister in law's crazy antics out of the way. Then, her numerous attempts to "push your buttons" in order to upset you won't work. She'll give it up eventually. Also , your being there, will also have an added benefit - it will help your brother to see his wife exactly as she is, doing these crazy things she insists on doing & subsequently he'll have a clearer picture of his own relationship with her - and who knows, maybe he can find some simple way this woman could be
reassured of her safety in her position in the relationship.
It's also good to remember that this "VELCRO STAGE" of all relationships when the couple behave as if they are inseparable - wears off in a year or two,
I think that your caring, concern for your brother are such loving & terrific intentions. My own family is so broken apart & distant from each other that we barely know one another. But then, God has put other people in my life who fulfill those roles more than adequately, not to mention my own family - my daughter's and grandchildren. I wish you and your brother all the best, I feel sure this will work out well for all concerned.