my friend

my friend xxxx is an amazing friend and she is always there to support me when times are tough. but my sister ******, whenever i am with xxxx always tries to cause an argument and always tries to wind me up in any way she can. i am worried that one day i wont have any friends at all, and it will all be because of *****.i really hate her at times because after whats been going on she just makes it all a hole load tougher, which it doesnt need to be. she makes it all so difficult and i dont know how much more of it i can take because she makes me so angry.