Help me with my so called bst friend?

ive got this only frnd of mine. she is selfish. she just uses me to alleviate her loneliness. she is too self centered to notice anything. whenever i try to tell her her flaws she just ignores. she is not ready to see her faults and is very smug. i am her only emotional support. she is kept apart in her family too sometimes, bcoz of her nature. she was so nice at the beginning but now when she is my best frnd she sucks the hell outta me. even in our cl everyone knows that we are bst frnds. i cant leave her bcoz i'll be left alone n she too. n i dont want that to happen.