my 17 year old sister (im 14 also girl) is insane. she cut her hair all off to above her ears and dyed it green. Now i noticed this was around the time everyone was busy celebrating me scoring a audition into a very good school for the arts. It may sound crazy but im not joking when i say she puposly screams out of no where and more things. advice
Unfortunately, this is part of having a sister. Siblings are always fighting over attention and what you described reminds me of my own childhood. It gets better as you guys get olde , don't worry. In the mean time, just hang in there.