Sister in law from hell

My sister in law only reaches out to me when she needs something. She never leaves me alone. She recently started seeing someone and she reaches out to me nearly every day asking if her relationship is similar to me and her husbands. I think it's weird that she asks such personal things about my husband and I. She asked me when we first slept together. I was appalled and told her it was none of her business. She also slept with my cousin before she started seeing this new guy, no matter what I do to keep her at arms length nothing works. We are both graduating the same time, she is graduating from undergrad and I am graduating from law school. She always contacts me with her issues about school, studying, her upcoming graduation and never bothers considering my stress and or what I'm going through. I understand that I am a couple of years older and she is immature but it is really hard. I do not get along with the rest of my in laws. I just feel emotionally exhausted. I don't have patience for one sided relationships.