To really help you you need to find the source of the problem, guessing lart of it might be your step sis. Sgut yourself in your room breath in deeply and then out keep going for 2 minutes while counting to ten. Imaging yoursefl in a happy place with the person you love the most. (the one who doesnt annoy you) relax your muscles and breath in again counting to ten once more. If you feel sleepy then you feel relax. If not then try again just forget all the thing that went wrong that day. As for you friend tell her it is annoying you and that you want her to stop but also noticed that she just wants you to be happy hozzie again.