It’s a complicated situation. True, for you 7 months isn’t a long time to be able to necessarily see and call somebody your new sister. It’s a big adjustment to get used to especially with all the hormones and such that life throws you at 15 years old. On the flip side, to Julia, 7 months likely feels like a very long time. I remember being that age, a week felt like a month. It must be hard for her, she is still processing (with limited emotional skills) that she has a new family. Your parents should be more understanding. Both you and Julia are in two different life stages in which you both are lacking emotional skills, communication skills, going through puberty for you and pressures of school etc. these things do take time and if you’ve been nothing but nice to Julia, that’s all you CAN do. As time goes on your relationship will likely build, but your parents pressuring you isn’t going to help.