How can I make my wife feel better ?

My wife is upset because she thinks I love my sister more than her. My sister wasn't feeling well all morning I been paying more attention to her she feels sad she thinks I love her more that's not true I love both of them but my sister needed me she said it's not fair she thought when we were married she have me all to herself she does most of the time. She also gets really worried about me. She can't leave me alone for 10 minutes she has to fallow me around everywhere even to work yet my boss doesn't care. I dont know why shes so worried about me for. She's been acting strange lately. how can I help her feel better ?