I cannot forgive my sister. Should I try harder?

Sister lives abroad thank goodness so I don't have to face her very often. Mum and Dad speak to her on the phone once every 2.5 weeks so clearly they are not that close. Phone calls typically last 6 minutes. 8 years ago she borrowed money from me and refused to pay it back when she promised. Only by my parents nagging did she finally pay it back without any apology to me. She is arrogant, bossy and always criticising and she likes to go one better e g. her friend will always have a bigger and newer car. I am sure you know the type. She feels excluded because parents are apparently always praising me. Mum told me I am her dearest friend. I have nothing in common with her but I feel that as my parents get older they don't like or want the conflict between their children. I detest the way she treated me as she betrayed my trust when I lent her the money plus she was not appreciative. Should I let it go as it is like a festering sore. She repaid the money 3 years ago but since then I have refused to see her when she comes home. However I feel that I should forgive her and I will have to do this without raising the loan as it will rake up the past. I want to at least be civil towards her and meet her when she next comes home. Is it possible to forgive without telling the person? Obviously I would change my behaviour towards her but we will never be close and in truth I don't like her. I feel she is jealous of me too as I have been successful in my business whereas she is on the verge of bankruptcy. Thank you for the answers but I have some more information to add. My sister just phoned my Mum today and Mum made a point of telling my sister who is 59 that we do mention her. This comment arose as a result of meeting some friends who had gone on holiday to the same place my sister lives so of course Mum said that my sister lived nearby etc. Why does Mum make a point of telling my sister that she talked about her? It is almost as if she is reassuring her that she is not out of sight and out of mind. I wonder if my sister finds it condescending to be told that by my mother as it is rather patronising? In a healthy relationship surely Mum would not need to say something so pointed. Any comments on this please.

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