Becky, I am so sorry that at a time in your life-you are pregnant!-when you should be floating on air, you are instead being so mistreated by your sister. I have some very unfortunate troubles with my family and my advice is to have as little contact as possible. It is obvious that you love your sister or else you wouldn't care so much about resolving this and understanding her point of view. But, if she cannot coherently and constructively explain her concern then her intentions may be simply to hurt you. Is it possible she is jealous of your situation? You may want to see and speak to her very little over the next few months. Are the other members of your family supportive?
My first and only child was born almost 16 months ago and my family made me feel absolutely horrible and completely stressed out during my pregnancy.All I can say is-don't worry. You will figure out how to take care of that baby. I had diapered a baby maybe two times before I had Joseph. I had no one to help me after my c-section because my husband had to go back to work after less than one week. Just read some books, take some classes and forget about it. You will know what to do. Tip: Throughout your pregnancy and after your baby is born drink as much water and get as much sleep as you possibly can. Also-if you want to breastfeed find someone who will not let you give up under any condition. Many of my friends gave up and I would have too had my husband not supported me completely.
Good luck with your sister. Has anything changed over the past week?