Problem with sister-in-law?

I am planning on returning to school to get my masters in nursing. For some unknown reason my S-I-L has decided to make my life hell for this. She lives in California, 2500 miles from me and is a Vet. It took her 15 years to do this. What ever, she finally did it, that is all that matters. I will have my masters in two years, hopefully less. My S-I-L has been calling and talking to me then she calls my husband and tells him that I belittled her or I hung up on her or something to that effect. My husband just ignores her. But it is really starting to make me angry. We have never had a good relationship. She has always felt I was never good enough for her brother. She says because of me he never got to go to college. My husband works for the railroad and they have put him thru schooling for his job, so I don't know where she has gotten this idea. I was an LPN before marriage, then I went back and got my bachlors for my RN and now I am going to get my masters. Any advise?